Immunoglobulins and variants directed against pathogenic microbes

ABSTRACT

Anti-microbial monoclonal antibodies and variant antibodies having a heavy chain constant regions with at least one amino acid substitution are provided. Such antibodies may be used to prevent or treat microbial infections.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No. 14/312,585, filed Jun. 23, 2014 and now pending; which is a continuation of International Patent Application No. PCT/US2012/071556, filed Dec. 23, 2012 and now expired; which claims priority to U.S. Provisional Application No. 61/580,194, filed Dec. 23, 2011 and now expired; the subject matter of all of which is hereby incorporated by reference as if fully set forth herein.

BACKGROUND

Pathogenic microbes, such as gram-positive cocci, can produce an array of secreted or cell surface-associated virulence factors, which are capable of interfering with the host immune responses. A number of such virulence factors are binding proteins, which contain one or more domains that bind to host immunoglobulins. Such Immunoglobulin binding virulence factors which bind to the heavy chain constant region of the immunoglobulin are referred to at Immunoglobulin Binding Proteins (IgBPs). A subset of Immunoglobulin Binding Proteins, which interact with the Fc region of immunoglobulins, are referred to as Fc Binding proteins (FcBPs). This non-immune binding of immunoglobulins by IgBPs involves regions of the immunoglobulin outside of the antigen-antibody combining site. Such non-immune binding of host immunoglobulins by microbial virulence factors is thought to subvert the host anti-microbial immune response. Functionally, this can occurs through immuno-shielding by coating of the bacteria with Fc bound antibody, by blocking immunoglobulin Fc-mediated effector functions such as complement activation or Fc-receptor mediated binding to effector cells, or by expression of superantigens which interact with immune cell surface receptors.

In the case of Staphylococcus aureus (S. aureus), a number of immunoglobulin binding proteins are expressed, including Protein A (SpA), Sbi, SSL7 and SSL10.

There is some evidence that it is possible to generate an antibody response to highly purified surface components of S. aureus such as capsular polysaccharide, the collagen-binding protein Cna and the fibrinogen-binding protein ClfA. This has led to the discovery and clinical testing of a number of antibodies based therapies directed against such S. aureus antigens.

Despite promising preclinical activity, clinical trials of such agents have been met with little success. Infants with very low birth weights (<1500 g; <32 weeks gestation) are at a particular risk for nosocomial bacterial infection, as they have not benefited from trans-placental transfer of maternal antibodies. Many of these infections are caused by S. aureus. Altastaph® is a vaccine-induced hyperimmune polyclonal antibody with specificity for S. aureus serotype 5 and 8, developed by Nabi Biopharmaceuticals (US20060153857 A1). In spite of reaching target serum antibody levels, no decrease in S. aureus infection rates was observed in treatment groups in two clinical trials (Rupp et al., 2007; DeJonge et al., 2007). A second anti-S. aureus human immune sera, INH-A21 (Veronate®) was prepared by first screening donors for high titres against MSCRAMM (microbial surface components recognizing adhesion matrix molecules), (Inhibitex—U.S. Pat. No. 6,692,739). Although Phase II trials appeared promising at the highest antibody dose, Phase III of the trial did not observe any effect of antibody treatment in reducing the frequency of S. aureus infection.

Additional antibodies or antibody derived molecules which have been under development include Aurograb, an antibody that targets the immunodominant ABC transporter in MRSA (Weems et al., 2006), which was designed to blocks the multi-drug efflux pump, allowing antibiotics to retain effectivity; tefibazumab (Aurexis®) (U.S. Pat. No. 6,979,446), which targets Clumping Factor A (ClfA) and pagibaximab (BYSX-A110, US20080019976 A1), a chimeric antibody which binds lipoteichoic acid (LTA) present in the membrane of gram-positive bacteria. Elusys Theraputics has also attempted to developed a bispecific heteropolymer antibody by cross-linking an antibody directed against SpA with a second antibody the recognizes the CR1 receptors (WO 2008/140487 A2).

Currently, none of the approaches described above have shown significant activity in clinical trials. The development of new antibody based agents which overcome microbial immune evasion for the treatment or prevention of microbial infections, including S. aureus, is an important goal that would be of great clinical benefit.

SUMMARY

The embodiments described herein provide for anti-microbial variant antibodies, which have attenuated non-immune binding (binding to residues outside of the antigen-antibody combining site) to one or more microbial immunoglobulin binding proteins (IgBPs).

According to the embodiments described herein, the disclosure provides anti-microbial monoclonal antibodies. In one embodiment, an anti-microbial variant antibody is provided that includes an immunoglobulin heavy chain (e.g., an IgG heavy chain) that differs from that of its unmodified parent anti-microbial antibody by at least one amino acid substitution, wherein the variant immunoglobulin heavy chain has attenuated non-immune binding to one or more microbial virulence factors as compared to that of the unmodified parent antibody. In one aspect, the variant anti-microbial IgG antibody includes a variant heavy chain, in which at least one amino acid from the IgG heavy chain constant region is substituted with another amino acid which is different from that present in the parent antibody.

In some embodiments, the monoclonal antibody is a chimeric, humanized of human anti-microbial IgG variant antibody, in which at least one amino acid from the IgG heavy chain constant region, is substituted with another amino acid which is different from that present in the parent antibody. Such variant anti-microbial antibodies have attenuated heavy chain constant region binding to one or more microbial IgBPs or IgBP domains expressed by the target microbe.

The variant immunoglobulin IgG heavy chain constant regions described herein can be combined with immunoglobulin variable heavy and light chain regions which bind antigens produced by microbes that express one or more microbial IgBP.

In some embodiments, the variable domain of the antibody binds to a microbial protein that is a microbial immunoglobulin binding protein, and the heavy chain constant region of the antibody is a variant which has attenuated binding to one or more microbial IgBPs or IgBP domains expressed by the target microbe.

In other embodiments, the variable domain of the antibody binds to a microbial protein that is not an microbial immunoglobulin binding protein, and the heavy chain constant region of the antibody is a variant which has attenuated binding to one or more microbial IgBPs or IgBP domains expressed by the target microbe.

The anti-microbial heavy chain constant region variant IgG immunoglobulins claimed herein have enhanced antimicrobial activity relative to their parental antibodies. For example, in the case of S. aureus, an important human pathogen for which there is an urgent unmet therapeutic need, a number of IgBPs can be expressed, including SpA, Sbi, SSL7 and SSL10.

In some embodiments the target microbe is S. aureus. Heavy chain constant region variant IgG immunoglobulins are described, which have attenuated binding to one or more S. aureus IgBPs due to the introduction of one or more amino acid substitutions in the heavy chain constant region domain relative to the parental IgG.

In some embodiments in which the target microbe is S. aureus, such heavy chain constant region variant IgG polypeptide sequences are combined with immunoglobulin heavy chain variable polypeptide sequences and light chains polypeptide sequences, which bind one or more cell surface or secreted S. aureus antigen.

In some embodiments, the S. aureus antigen recognized by the variable domain of variant antibodies are cell surface or secreted antigens selected from the list which includes but is not limited to: ClfA, ClfB, Cna, Eap, Ebh, EbpS, FnBPA, FnBPB, IsaA, IsaB, IsdA, IsdB, IsdH, SasB, SasC, SasD, SasF, SasG, SasH, SasK, SdrC, SdrD, SdrE, Spa, SraP, Coa, Ecb, Efb, Emp, EsaC, EsxA, EssC, FLIPr, FLIPr like, Sbi, SCIN-B, SCIN-C, VWbp, SpA, LTA, CP5, CP8, PNAG, dPNAG, alpha toxin, CHIPS, PVL leukocidin, α, β and γ-hemolysins, SAK, Sea, Sep, Seb, Epa, Efb, SCIN, Exfoliatins ETB and ETA, Staphylococcal Enterotoxins SEA, SEB, SECn, SED, SEG, SHE, and SEI, Toxic-shock syndrome toxin TSST-1, Alpha Toxin, Beta toxin, Delta toxin.

In some embodiments, the antigen recognized by the variable domain of the antibody or its heavy chain constant region variants is S. aureus SpA. In such embodiments, the microbial antigen recognized by the variable domain of the variant IgG antibody is an epitope found in one or more of the repeat homology IgBP domains of S. aureus SpA (referred to as SpA domains E, D, A, B, and C).

In some embodiments, the antigen recognized by the variable domain of the antibody or its heavy chain constant region variants is S. aureus Sbi. In such embodiments, the antigen epitope recognized by the variable domain of the antibody or its variants is located in one or more of the Sbi IgBP binding domains I and II.

In some embodiments, the antigen epitope recognized by the variable domain of the antibody or its heavy chain constant region variants is found in two or more of the repeat IgBP homology domains of SpA or Sbi, selected from the list SpA domains E, D, A, B, and C, and Sbi domains I and II.

In some embodiments, the antigen epitope recognized by the variable domain of the antibody or its heavy chain constant region variants is found in one more of the repeat IgBP homology domains of both SpA and Sbi, selected from the list SpA domains E, D, A, B, and C, and Sbi domains I and II.

Described herein are methods of producing monoclonal antibodies that recognize SpA and/or Sbi, methods for selecting antibodies that cross react with multiple SpA IgBP domains (selected from SpA domains E, D, A, B, and C) and/or Sbi (selected from Sbi domains I and II), methods of selecting antibodies that cross react with one or more SpA IgG binding domains and Sbi domains I and/or II, methods of assaying for antigen binding to SpA or Sbi using variant IgG1 antibodies, having one or more amino acid substitutions in the heavy chain constant region which prevent heavy chain constant region binding to SpA, Sbi or SSL10. In some aspects, the variant Fc domain used for antibody selection is of human isotype IgG1 having one or more of the following amino acid substitutions: a His to Arg substitution at position 435, a Tyr to Phe substitution at position 436 and a Arg to Gln at position 274. In one aspect, the variant Fc domain used for antibody selection is of human isotype IgG1 and has a His to Arg substitution at position 435, a Tyr to Phe substitution at position 436 and a Arg to Gln at position 274. In another aspect, the variant Fc domain used for antibody selection is of human isotype IgG1 and has a His to Arg substitution at position 435. The uses of such Fc variants are important so as to differentiate antigen specific binding of the antibody from Fc mediated binding to Sbi and or SpA (positions refer to EU numbering).

In an additional embodiment, modification of human or humanized VH3 family derived anti-S. aureus IgG variable heavy domain residues are claimed which abrogate superantigen type binding of SpA to anti S. aureus immunoglobulins or their heavy chain constant region variants.

In an additional embodiment, the antigen recognized by the variable domain of the claimed heavy chain constant region variant immunoglobulins is S. aureus Clumping factor A (ClfA).

In additional embodiments, heavy chain constant region variant anti-S. aureus antibodies are provided in which the human, humanized, or chimeric variable domain, or variable domain CDRs of the antibody are derived from an anti-S. aureus antibodies selected from the list: Pagibaximab (a chimeric anti-LTA antibody; Biosynexus/Medimmune), Tefibazumab (a humanized IgG1 anti-ClfA; Aurexis, Inhibitex/BMS), CS-D7 (human anti-IsdB IgG1, Merck), Aurograb (scFv fragment anti ABC transporter; NeuTec/Novartis), anti-Alpha toxin (Medimmune patent application WO/2012/109285).

In other embodiments, affinity matured heavy chain constant region variant anti-S. aureus antibodies are provided in which human, humanized, or chimeric variable domain of the antibody are derived from an anti-S. aureus antibodies selected from the list including, but not limited to: Pagibaximab (a chimeric anti-LTA; Biosynexus/Medimmune), Tefibazumab (a humanized IgG1 anti-ClfA, Inhibitex/BMS), CS-D7 (a humanized anti-IsdB IgG1, Merck), Aurograb (an scFv fragment anti-ABC transporter; NeuTec/Novartis), anti-Alpha toxin (Medimmune patent application WO/2012/109285). Such claimed affinity matured Heavy chain constant region variant antibodies have at least one amino acid substitution, deletion or insertion relative to the parental heavy or light chain variable domain sequences.

In additional embodiments, the disclosure also relates to the prophylactic or therapeutic use of such anti-microbial immunoglobulins and their heavy chain constant region variants, and their use in combinations with additional antimicrobial chemotherapy or anti-infective agents or in combination with one or more additional antimicrobial immunoglobulins or variant immunoglobulins.

The disclosure also relates to the prophylactic or therapeutic use of such anti-microbial immunoglobulins and their heavy chain constant region variants, and their use in combinations with additional antimicrobial chemotherapy or anti-infective agents or in combination with one or more additional antimicrobial immunoglobulins or variant immunoglobulins for use in veterinary or animal use.

The anti-microbial heavy chain constant region variants immunoglobulins described herein, which have enhanced anti-microbial activity relative to their parental antibodies, may be used for the prophylactic or therapeutic treatment of a number of important infectious diseases.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the domain organization of an IgG polypeptide according to some embodiments.

FIG. 2 is a schematic diagram illustrates the domain organization of the SpA (SpA) polypeptide (Panel A) and shows the sequence alignment of the five highly homologous extracellular Ig-binding domains of SpA in tandem, designated domains E (SEQ ID NO: 67), D (SEQ ID NO: 66), A, B, and C (Panel B).

FIG. 3 is a schematic representation of a complex between SpA domain D and Fab 2A2 from a human IgM. (Panel A) shows a side view of SpA domain D bound to the framework region of the Fab heavy chain. The VL domain, which is not involved in this interaction, is shown on the right. The CDR loops as defined by Chothia and Lesk are highlighted at the top. (Panel B) shows a schematic diagram detailing the residues of SpA domain D and Fab 2A2 involved in the interaction. Kabat numbering is used for the VH residues; domain D is numbered with the convention used for SpA domains.

FIG. 4 is a schematic diagram illustrating the SpA (top) and Sbi (bottom) polypeptide domain organization.

FIG. 5 shows a sequence alignment of human IgG sequences IgG1, IgG2, IgG3 and IgG4 for the CH1 region (SEQ ID NOS: 68-71), the Hinge Sequence (SEQ ID NOS: 72-75), the CH2 sequence (SEQ ID NOS: 76-79) and the CH3 sequence (SEQ ID NOS: 80-83).

FIG. 6 is a table showing Human IgG1 allotypes.

FIG. 7 illustrates the allotypes of the gamma chain of human IgG3. The positions of amino acid substitutions in the gamma chain of IgG 1, 2 and 4 are compared to IgG3 allotypes.

FIG. 8 illustrates domain B of Spa with inter-domain substitutions. Panel A shows domain B of SpA interacting with an IgG Fc domain. Inter-domain substitution positions are shown in yellow and by arrows. Panel B shows a close up of the interaction of SpA domain B with the IgG constant region. The structure encompasses the IgG CH2-CH3 interface. Alpha Helices are shown as cylinders (within the circle). SpA Helix I and II (Helix III is not shown), which form the binding interface with residues within the IgG CH2-CH3 region, are shown. Amino acids of the backbone (worm representation) and side chains which vary between domains B and domains E, D, A and C (FIG. 2) are shown in yellow and by arrows. Diagram made using Cn3D using and PDB ID 1FC2).

FIGS. 9A-9C are a series of diagrams showing domain D of SpA interacting with the Fab domain of a human IgM. FIG. 9A shows Domain D of SpA interacting with the Fab domain of a human IgM. The diagram is adapted from Grille, et al., 2000 using Cn3D (PDB ID: 1DEE). Helix II and III, which form the binding interface with residues within the VH3 Fab, are shown. Amino acid backbone (worm representation) and side chains are shown. The position of amino acids which vary between domains E, D, A, B, and C (FIG. 2) are shown in yellow (inter-domain substitutions). The contact residues which form the binding interface are conserved among all SpA Ig-binding domains, suggesting that each could bind in a similar manner. FIGS. 9B and 9C show close ups of the interactions from different angles.

FIG. 10 models a Q to K substitution at amino acid 45 of SpA domain E. Amino acid K is found at the same position in all sequenced stains of S. aureus domains D, A, B and C that were analyzed (FIG. 11). The position of the Q to K substitution in domain E (yellow), is located on the face of Helix II that does not interact with the VH3 Fab from human IgM.

FIGS. 11A-11E (SEQ ID NOS: 84-151) show the amino acid sequence alignment of individual SpA IgBP domains A-E, respectively, from sequenced stains of S. aureus. The position of intra-SpA domain substitutions found in different S. aureus stains are indicated with an arrow. If the substitution is found in one or more of the other SpA domains, it is indicated under the arrow. For example, the SpA A domain of S. aureus stain CC45_A9635 has and E to D substitution at residue #8 (FIG. 11A). Residue D is found at the homologous position of SpA domain D in all sequenced stains of S. aureus (amino acid position 11 in domain D).

FIG. 12 illustrates the domain structure of SpA and Sbi in Panel A. Domains I and II of Sbi have homology to SpA IgBP domains. Panel B (SEQ ID NOS: 152-156) shows the amino acid sequence of domains E, D, A, B and C (Kim et al., 2010). Helix regions (see FIGS. 8 and 9) are labeled H1 (Helix I), 2 (Helix II) and 3 Helix III). The amino acid sequence of domains I and II of Sbi are shown (SEQ ID NOS: 157-158). Similarity analysis of Sbi domains I and II are shown above the Sbi sequences. Amino acids that are conserved between Sbi domains I and II and SpA IgBP domains are shown below the Sbi amino acid sequences.

FIG. 13 The IgFc binding domains of Sbi (I and II: FIG. 12) were analyzed. Amino acids within Helix I are highly conserved between Sbi domains I and II. Conservation is also found between Sbi domains I and II and SpA Fc binding domains within SpA helix I, and a number of amino acids in SpA Helix II (* in FIG. 12B). Invariant residues (conserved in SpA domains and Sbi domains I and II) were mapped onto the model of Spa domain B (Helix I and II shown) binding to the Fc region of IgG. Important residues (yellow residues and arrows) that interact with Fc domain are conserved between SpA domains and Sbi domains. In addition to these invariant residues, a number of residues are found in Sbi domains I and II that are present in some SpA domains (FIG. 12). Thus, the Fc binding interface of Sbi and SpA has a high degree of conservation.

FIG. 14 (SEQ ID NOS: 159-180) shows the amino acid sequence of the individual Sbi IgBP domains from sequenced stains of S. aureus. Panel A illustrates multiple sequence alignment of Sbi domain I. Panel B illustrates multiple sequence alignment of Sbi domain II.

FIG. 15 models the IgFc binding domains of Sbi (Domains I and II: FIG. 14), using the structure of SpA domain B. Sbi was analyzed for inter-strain substitutions within domains I and II. One Sbi amino acids within Domain I of strain CC239_JKD6009 was found to differ. This substitution (yellow residue and arrow in FIG. 15) is located in the predicted Helix I of Sbi. This position is not conserved between Sbi domains I and II. The position of this substitution (amino acid N to S substitution) was mapped onto the model of SpA domain B (Helix I and II shown) binding to the Fc region of IgG. As shown, the residue (yellow residue and arrow) is not predicted to form an interaction with the Fc domain.

FIG. 16 is an SDS-PAGE and Western blot of anti-SpA parental antibody MAB1 (upper panels) and anti-SpA-variant antibody MAB2 (Lower panels).

FIG. 17 is an SDS-PAGE and Western blot of anti-ClfA parental antibody MAB3 (upper panels) and variant antibody MAB4 (Lower panels).

FIG. 18 is an SDS-PAGE and Western blot of anti-RSV variant antibody MAB5.

FIG. 19 shows constructs used for DLS and immune-diffusion studies. The following S. aureus SpA and Sbi IgBPs proteins or their domains have been used to characterize S. aureus IgBP binding to variant and parental heavy chain constant region sequences. Purified constructs have been used for immunodiffusion and Dynamic Light Scattering experiments.

FIG. 20 shows an immuodiffusion analysis of antibodies MAB1, MAB2 and MAB5 with SpA and Sbi-E.

FIG. 21 shows an immuodiffusion analysis of antibodies MAB1, MAB2 with SpA domain D and Sbi-domains II/IV.

FIG. 22 shows an anti-RSV variant MAB5 analysis by DLS. The left panel shows the analysis of the control anti-RSV variant antibody alone (MAB5). The right panels show the size distribution in the presence of either Sbi-E (fragment of Sbi containing the two Ig-binding domains and two complement binding domains) or SpA1-4 (SpA IgBP domains 1-4).

FIG. 23 shows an anti-SpA parental MAB1 analysis by DLS. The left panels shown the analysis of the parental anti-SpA antibody (MAB5) alone (upper panel) or with Sbi III/IV (fragment of Sbi containing the two complement binding domains (lower panel)). The right panels show the size distribution in the presence of either SpA 1-4 (SpA IgBP domains 1-4) or Sbi-E (fragment of Sbi containing the two Ig-binding domains and two complement binding domains).

FIG. 24 illustrates a time dependent DLS peak shift with MAB1 and SpA-2. The left panel shown the analysis of the parental anti-SpA antibody alone (MAB1). The left panels show the size distribution in the presence of either SpA-2 (fragment of SpA containing domain D) after 1 min (upper panel) or 10 mins incubation (lower panel).

FIG. 25 shows an anti-SpA variant MAB2 analysis by DLS. The left panels shown the analysis of the variant anti-SpA antibody (MAB2) alone (upper panel) or with Sbi-E (fragment of Sbi containing the two Ig-binding domains and two complement binding domains (lower panel)). The right panels show the size distribution in the presence of SpA 1-4 (SpA IgBP domains 1-4). The lower left panel shows the overlap of the MAB2 control plot (red) and the MAB2 plot in the presence of SpA 1-4 (green).

FIG. 26 shows an anti-SpA variant MAB2 analysis by DLS-Single SpA domain. The upper panels shown the analysis of the variant anti-SpA antibody (MAB2) alone or with SpA-2 (SpA domain D).—lower panel.

FIG. 27 shows an analysis of binding of antibodies to S. aureus Newman and a S. aureus SpA delation stain in the absence and presence of blocking human IgG1Fc. Antibodies tested include anti-SpA MAB1, anti-SpA variant MAB2, anti-CIfA Parental MAB, anti-RSV variant MAB5 and a non-specific anti-KLH antibody. In the left panels, antibodies are tested in the absence of hIgG1 Fc. The upper panels represent binding to a S. aureus stain lacking expression of SpA (delta SpA=ΔSpA). The lower panels represent binding to S. aureus Newman stain. Blank contains no primary antibody.

FIG. 28 shows tabulated results of ELISA binding of antibodies and their variants to a S. aureus stain lacking expression of SpA (Yellow panel: ΔspA) and to S. aureus Newman stain (Pink Panel: Newman) in the presence (Red bars) or absence (Blue bars) of human IgG1-Fc.

FIG. 29 shows a FACS analysis of antibody Binding to S. aureus: Binding of the parental anti-SpA antibody (MAB1), an example anti-SpA variant antibody (MAB2) and a heavy chain constant region matched anti-RSV variant control antibody (MAB6) were investigated by FACS, using S. aureus Newman strain (upper panels) or a ΔSpA strain (lower panels)) grown to log phase (left panels) or from stationary phase cultures (right panels).

FIGS. 30A and 30B show antibody mediated C1q deposition: FACS analysis was performed to test whether the parental anti-SpA antibody MAB1 (center panel), its variant anti-SpA antibody MAB2 (right panel), or the control anti-RSV variant antibody MAB5 (left panel) antibodies are able to deposit C1q on wild type S. aureus Newman (FIG. 30A) or a S. aureus ΔSpA stain (FIG. 30B). The upper panel of FIGS. 30A and 30B use an anti-hC1q detection antibody, while the lower panels use a negative control detection antibody. Three concentrations of each antibody are shown for each Histogram: 3.33 μg/ml (red), 10 μg/ml (blue) and 30 μg/ml (green).

FIG. 31 shows a tabulation of antibody mediated C1q deposition data. The data from the FACS Histograms in FIG. 30 are tabulated. The Y axis shows % stained bacterial population.

FIG. 32 shows a C3 complement deposition assay on Staph JE2 using FACS. C3 deposition on the surface of S. aureus stain JE2 was tested using the anti-SpA parental antibody (MAB1: Red plot) and an example anti-SpA variant antibody (MAB2; Green Plot).

FIG. 33 illustrates neutrophil-mediated opsonophagocytic activity of anti-SpA antibodies. The anti-SpA parental antibody (MAB1-Green plot) and an example variant anti-SpA antibody (MAB2—pink plot) were tested in phagocytosis assay using S. aureus Newman stain (left panel) and a ΔSpA strain lacking SpA expression (right panel). Control anti-RSV variant (MAB5-Blue plot) and anti-KLH antibodies (Red Plot) are used as negative controls. Phagocytosis of FITC labeled S. aureus was analyzed by FACS.

FIG. 34 shows an opsonophagocytic assay of anti-SpA antibodies.

Opsonophagocytic assay of MAB1 and MAB2 using S. aureus JE2 was determined in a second Opsinophagocytic assay. % Bacterial survival (Y axis) was measured for S. aureus JE2 following treatment with MAB1 (dark bars) and MAB 2 (light bars) using 5 ug/ml and 25 ug/ml of test antibody. A control (no antibody) is shown on the left side (grey bar)

FIG. 35 shows a neutrophil-mediated opsonophagocytic bactericidal assay. Opsonophagocytic killing of S. aureus JE2 using pooled human serum. Parental anti-SpA MAB1 (Dark Bars) and an example variant anti-SpA MAB2 (light bars) were tested for their effect on the opsonophagocytic killing of S. aureus JE2 using 5 μg/ml (left bar of pair) and 25 μg/ml (right bar of pair) of test antibody.

FIG. 36 shows the amino acid sequence of the light chain (SEQ ID NO:58) and heavy chain SEQ ID NO:59) of a CS-D7 parental monoclonal antibody.

FIG. 37 shows the amino acid sequence of three light chains (SEQ ID NOs:60-62) and three heavy chains (SEQ ID NOs:63-65) of an anti-LTA parental monoclonal antibody.

DETAILED DESCRIPTION

Antibodies and variant antibodies that may be used to reduce, treat or eliminate pathogenic microbes and/or associated virulence factors are provided herein. The variant antibodies described herein have enhanced antimicrobial activity relative to their parent antibody. In some embodiments, the enhanced antimicrobial activity is due to at least one amino acid substitution as compared to the parent antibody that gives rise to a variant heavy chain constant region, a variant variable region, or both. As described below, such variant constant and variable regions may result in attenuated non-immune binding to one or more virulence factors produced by a targeted pathogenic microbe. Virulence factor binding that may be affected by the variant heavy chain constant and heavy chain variable regions described herein include virulence factors that involve non-immune binding to an antibody (e.g., immunoglobulin binding proteins (IgBPs), Fc binding proteins (FcBPs) and superantigens which interact with the Fab domain). Variant antibodies of the invention are directed against microbial antigens, including virulence factors and IgBPs. Antibodies and variant antibodies described herein can be affinity matured, resulting in enhanced antigen specific immune binding.

Microbial Targets

The antibodies and variant antibodies described herein may be designed to target the effector function of any pathogenic microbe including, but not limited to, bacteria (e.g., bacteria from the following genare: Bordetella, Borrelia, Brucilla, Campylobacter, Chlamydia, Chlamydophila, Clostridium, Corynebacterium, Enterococcus, Escherichia, Francisella, Haemophilus, Helicobacter, Legionella, Leptospira, Listeria, Mycobacterium, Mycoplasma, Neisseria, Pseudomonas, Rickettsia, Salmonella, Shigella, Staphylococcus, Streptococcus, Treponema, Vibrio, Yersinia), viruses (e.g. Adenovirus, Coxsackievirus, Epstein-Barr virus, Hepatitis A virus, Hepatitis B virus, Hepatitis C virus, Herpes simplex virus, type 1, Herpes simplex virus, type 2, cytomegalovirus, Human herpesvirus, type 8, HIV, Influenza virus, measles virus, Mumps virus, Human papillomavirus, Parainfluenza virus, Poliovirus, Rabies virus, Respiratory syncytial virus, Rubella virus, Varicella-zoster virus), and parasites (e.g., Acanthamoeba, Anisakis, Balantidium coli, Entamoeba histolytica, Giardia lamblia, Leishmania, Plasmodium falciparum, Schistosoma, Toxoplasma gondii, Trypanosoma).

In certain embodiments, the antibodies and variant antibodies may be designed to target the pathogenic gram positive bacteria, such as Staphylococci aureus (S. aureus) and group A Streptococcus (GAS). S. aureus and GAS are prominent Gram-positive human pathogens responsible for a wide spectrum of superficial and invasive disease conditions (Nizet, 2007). S. aureus accounts for >10 million skin and soft tissue infections annually in the United States alone1 and is the single leading cause of hospital acquired infections. Each year worldwide, GAS is responsible for more than 700 million cases of pharyngitis or skin infection and more than 650,000 invasive infections. Both pathogens can produce infections in essentially every human organ or tissue, including severe life-threatening conditions such as necrotizing fascitis, endocarditis, sepsis, and toxic shock syndrome. The propensity of S. aureus and GAS to produce systemic infections, often in otherwise healthy children and adults, defines a capacity of each pathogen to resist host immune clearance mechanisms that normally function to prevent microbial dissemination beyond epithelial surfaces. S. aureus and GAS systemic disease reflects diverse abilities of these pathogens to resist clearance by the multifaceted defenses of the human immune system. The mechanisms by which S. aureus and GAS avoid the bactericidal activities of cationic antimicrobial peptides, delay phagocyte recruitment, escape neutrophil extracellular traps, inhibit complement and antibody opsonization functions, impair phagocytotic uptake, resist oxidative burst killing, and promote phagocyte lysis or apoptosis have been reviewed by Nizet (Nizet, 2007).

S. aureus causes a variety of suppurative (pus-forming) infections and toxinoses in humans. It causes superficial skin lesions such as boils, styes and furuncules; more serious infections such as pneumonia, mastitis, phlebitis, meningitis, and urinary tract infections; and deep-seated infections, such as osteomyelitis and endocarditis. S. aureus is a major cause of hospital acquired (nosocomial) infection of surgical wounds and infections associated with in dwelling medical devices. S. aureus causes food poisoning by releasing enterotoxins into food, and toxic shock syndrome by release of superantigens into the blood stream. Although methicillin-resistant S. aureus (MRSA) have been entrenched in hospital settings for several decades, MRSA strains have recently emerged outside the hospital becoming known as community associated-MRSA (CA-MRSA) or superbug strains of the organism, which now account for the majority of staphylococcal infections seen in the ER or clinic. S. aureus permanently colonizes the moist squamous epithelium of the anterior nares of 20% of the population, and is transiently associated with another 60%. Occasionally, the organism can cause superficial skin infections such as abscesses and impetigo, or serious invasive infections such as septic arthritis, osteomyelitis and endocarditis. Colonization is a known risk factor for invasive disease both in the hospital and the community. Hospital patients who have been catheterized or who have undergone surgery are at increased risk of infection. Treatment of infections with antibiotics has become increasingly difficult owing to the widespread occurrence of strains that are resistant to multiple antibiotics, known as meticillin (formerly methicillin)-resistant S. aureus (MRSA). Furthermore, the isolation of MRSA strains that have also become resistant to vancomycin, the last drug to which the organism had been uniformly sensitive, raises the spectre of a return to the pre-antibiotic era.

The pathogenicity of S. aureus is a complex process involving a diverse array of extracellular and cell wall components that are also coordinately expressed during different stages of infection (i.e. colonization, avoidance of host defense, growth and cell division, bacterial spread). The coordinated expression of diverse virulence factors in response to environmental cues during infections (e.g. expression of adhesins early during colonization vs. production of toxins late in infection to facilitate tissue spread) suggests the existence of global regulators in which a single regulatory determinant controls the expression of many unlinked target genes (FEMS Immunol Med Microbiol. 2004 Jan. 15; 40(1):1-9). Bacteria use quorum sensing to synchronize release of these molecules. Individual bacteria secrete small molecules termed “auto-inducers” (A1), including N-acyl homo-serine lactones (gram-negative bacteria) and oligopeptides (gram-positive bacteria), at a constant, low level as a means of detecting the local concentration of bacteria.

An individual who has suffered from a S. aureus infection is usually not protected from a subsequent infection. This is because the host is prevented from mounting a strong antibody response, and immunological memory is compromised by the immunosuppressive activities of Vβ binding superantigens (Enterotoxin B, TSST-1, SAC1-3) and by nonspecific polyclonal B cell receptor activation resulting from binding of SpA to the B cell receptor Ig heavy-chain gene products of the VH3 family. In one such embodiment, the antibodies may be designed to target Staphylococci aureus (S. aureus).

Virulence Factors and their Effect on the Immune Response

The antimicrobial effector functions of antibodies are the target of a number of microbial immune evasion strategies, which have evolved to evade the immune response to the pathogen. These molecules, which are responsible for immune evasion, belong to the family of microbial virulence factors.

An immune response to a foreign antigen includes the production of antibodies by B-cells of the immune system against the foreign antigens that are detected within the body. Pathogenic microbes are one source of foreign antigens, which can stimulate the production of antibodies. A successful humoral immune response against such a pathogen results in the production of high affinity antibodies against the microbe, which are able to contribute to the elimination of the infection due to the effector function of the antibody. However, as described in detail below, a variety of pathogenic microbes (e.g., Staphylococci and Streptococci) produce a variety of virulence factors, which, among other functions, are able to attenuate the immune response against the microbe.

Virulence factors refer to microbial proteins or molecules (i.e., gene products) that enable a pathogen to establish itself on or within a host of a particular species and enhance its potential to cause disease. Most bacterial virulence genes involved in pathogenesis encode proteins that are either displayed on the bacterial surface (e.g. cell surface proteins) or are released into the surroundings (e.g. toxins and enzymes) and confers resistance to antimicrobials, which may strengthen its virulence and confer resistance to all families of antibiotics. These enable the organism to evade host defenses, to adhere to cells and the tissue matrix, to spread within the host and to degrade cells and tissues, for both nutrition and protection. These accessory genes are collectively known as the virulon (Novick 2003).

In one embodiment, a variant antibody has attenuated binding to a virulence factor when it binds the virulence factor in a non-immune fashion, i.e., the antibody binds the one or more virulence factor via a portion of the antibody that is not involved in antigen-dependent binding to the variable region of the antibody (e.g., Fc region binding or superantigen type Fab binding). In another embodiment, an antibody or variant antibody has enhanced antigen dependent immune-binding to a virulence factor when it binds the virulence factor in an immune fashion, i.e., the antibody or variant antibody binds a virulence factor in an antigen-dependent manner, via binding to the variable region of the antibody. Such antibodies and their variants can undergo affinity maturation when their antigen-dependent binding is enhanced by one or more amino acid substitution within the variable domain. These altered binding properties of the variant antibodies are not mutually exclusive. In other words, a variant antibody may have one or more amino acid substitutions (described below) that result in both attenuated non-immune binding to one or more IgBP virulence factors, and enhanced immune-binding to one or more virulence factors or microbial antigens.

Microbial proteins that contribute to the virulence of microbes such as S. aureus can be divided into at least five major families (described below): immune response inhibitors, superantigens, adhesion proteins, toxins, and enzymes. These virulence factor families are described below.

Immune Response Inhibitors.

Many bacteria produce virulence factors that inhibit the host's immune system defenses. For example, a common bacterial strategy is to produce IgBPs that bind to the Fc region of host immunoglobulin. Such IgBPs bind to the Fc region via non-immune binding. The best studies examples of FcBPs are SpA and Protein G (Goward et al., 1993; Bjorck et al., 1984, Reis et al., 1984), which are described in detail below. Additionally, the polysaccharide capsule coating the microbe can prevent effective elimination by host immune system effector cells.

Microbial IgBPs.

The non-immune binding of antibodies by bacterial or viral immunoglobulin IgBPs and FcBPs is a common strategy employed by pathogens to subvert the host immune response. The capacity of microorganisms to bind IgG or IgA via the Fc region has emerged as a widespread biological phenomenon. Immunoglobulin FcBPs are expressed on the cell surface of many Gram-positive pathogenic bacteria and are able to bind to Igs in a non-immune manner. In many cases, the Fc binding function has been incorporated into a larger multifunctional protein, which can have a number of virulence functions. The role of these proteins is almost certainly to help the bacteria adhere to host surfaces and to evade the immune response by allowing host proteins to cover the bacterial cell surface. Two of the first such proteins to be recognized were SpA (also referred to as Protein A), a cell-wall component of S. aureus, and Protein G, a protein associated with the cell walls of certain Streptococci. The Fc Binding Protein, SpA of S. aureus, serves to block Fc-receptor mediated effector functions such as opsonophagocytosis and contributes to virulence (Palmqvist et al., 2002). SpA binds the Fc region of IgG (Uhlen et al., 1984) and prevents both opsonophagocytosis and complement fixation (Gemmell et al., 1991).

Such FcBP proteins are also found among bacteria including streptococci of groups A, C, and G (Kronvall, 1973; Schroder et al., 1986), and Staphylococci (Forsgren & Sjouist, J Immunol. 1966). Furthermore, IgG FcBPs have been demonstrated on cells infected with Herpes simplex virus (Watkins, 1964; Chapman et al., 1999) of both serotypes I and 2 (Para, 1982), Varicellazoster (Ogata & Shigeta, 1974), Epstein-Barr virus (Yee et al., 1982) and Cytomegalovirus (Furatawa et al., 1975; Keller et al., 1976; Sprague et al., 2008; Lilley et al., 2001), Hepatitis C virus (Maillard et al., 2004), as well as on cells infected with schistosomes (Torpier, 1979).

Examples of such Fc Binding proteins (reviewed in Sidorin and Solov'eva, 2011) include, but are not limited to, Protein G from group C and group G streptococci (Derrick, 1992; Bjorck, 1984; Reis et al., 1984); β protein and M or M like family FcBPs such as Protein H, Arp4, Arp 60, Mrp4, Sir22, Enn4, FgBP (Kazeeval & Shevelev, 2009; Pleass et al., 2001; O'Toole et al., 1992; Heden et al., 1991; Jerlstro et al., 1991; Lewis et al., 2008; Meehan et al., 2001); SibA from GAS (Fagan et al., 1991); SpA from S. aureus (Boyle 1990 in Bacterial Immunoglobulin-Binding Proteins, ed. Boyle, M. P. D. (Academic, San Diego), Vol. 1, pp. 17-28, Gouda et al., Biochemistry. 1992 31:9665-7; Goward et al., 1993); SSL family members including SSL 7 and SSL10 from S. aureus (Ramsland et al., 2007; Kazeeval & Shevelev 2009; Ramsland et al., 2007); Sbi from S. aureus (Burman et al., 2008, Itoh et al., 2010); IsaB from S. aureus (Clark et al., 1999); PsaA from Y. Pestis; Eib-proteins from E. Coli (Sidorin. and Solov'eva, 2011).

It has been demonstrated that there is a striking overlap of the Ig Fc regions recognized by distinct bacterial IgBPs proteins, despite the fact that they derive from very different microbes (e.g. streptococcal and staphylococcal strains) and these microbes are pathogenic in different mammalian species. Even more remarkably, the fact that unrelated IgG binding proteins (e.g. SpA, Protein G) bind to similar sites in the IgG interdomain region parallels the situation for the unrelated bacterial IgA binding proteins (e.g. Sir22 from S. pyogenes, β-protein from group B streptococcus, and SSL7 from S. aureus), which all bind to the Fc domain interface in human IgA (Pleass et al., 2001; Wines et al., 2006; Ramsland et al., 2007). Although a different immunoglobulin class is involved, FcBP proteins produced by very different bacterial pathogens target the equivalent Fc region. Thus, it seems that convergent evolution may have favored the appearance of bacterial proteins that bind to the CH2/CH3 interface in IgG and IgA. This interdomain region in IgG, has been recognized as one of only a limited number of regions on the Ig surface that is particularly suited to protein-protein interactions (Burton, 1985; DeLano et al., 2000). For example, purified IgG Fc binding protein (FcBP) from the M15 strain of group A streptococci binds to the same site in the interface between the CH2 and CH3 domains as SpA, Protein G (SPA) (Nardella et al., 1985; Nardella et al., 1987) and IgG rheumatoid factors. His 435 and Tyr 436 on the IgG heavy chain, and possibly one or both of His 433 and 310, were demonstrated to be involved in the binding. The importance of His 435 in binding of many FcBPs to IgG originated with the findings on the specificity of IgG isotypes and allotypes for SpA. It was found that human IgG3 allotypes with Arg at position 435 lack the ability to bind SpA (Recht et al., 1982; van Loghem et al., 1982). IgG3 allotypes and IgG isotypes capable of binding SpA possess a His residue at position 435 within the interaction site for SpA. However, allotypes, which carry an Arg at this important CH3 domain residue, are unable to bind SpA (Recht et al., 1982; van Loghem et al., 1982).

Lack of Fc binding of antibodies to SpA has been used to develop a number of applications, including antibody based diagnostic tests for S. aureus Infection (Larsson & Sjoquist, 1989). In such cases, chicken or mouse immunoglobulin of non-binding isotypes can be used for the selective testing for S. aureus SpA by immune-assays.

The evolutionary reasons why such sites of relative vulnerability have been retained on the surface of Ig Fc regions probably relate to their role as interaction sites for important host receptors. In IgG, for example, the Fc interdomain region forms the interaction site for FcRn, the so-called neonatal Fc receptor that mediates a number of processes fundamental to IgG function, including regulation of IgG turnover and transepithelial transfer of IgG. It has been shown that the same residue at position 435 is important for FcRn binding. Its mutation (H435A) results in loss of binding of the antibody to both human and mouse FcRn.

Superantigens.

Superantigens (SAgs) are a class of antigens, which cause non-specific activation of T-cells or B-cells, resulting in polyclonal T or B cell activation. SAgs can be produced by pathogenic microbes (including viruses, mycoplasma and bacteria) (Llewely, 2002) as a defense mechanism against the immune system, and bind to antibodies via non-immune binding.

Superantigens are microbial or viral toxins that comprise a class of disease-associated, immunostimulatory molecules and act as Vβ-restricted extremely potent polyclonal T cell mitogens. They bind major histocompatibility complex (MHC) class-II molecules without any prior processing and stimulate large number of T cells (up to 20% of all T cells) on the basis of epitope specified by this receptor (Papageorgiou & Acharya, 2000; Acharya et al., 1994; Haynes & Fauci 2005). These properties are attributable to their unique ability to cross-link MHC class II and the T cell receptor (TCR), forming a trimolecular complex. The large number of activated T-cells generates a massive immune response, which is not specific to any particular epitope on the SAg thus undermining one of the fundamental strengths of the adaptive immune system, that is, its ability to target antigens with high specificity. More importantly, the large numbers of activated T-cells secrete large amounts of cytokines, which can cause severe and life-threatening symptoms, including shock and multiple organ failure.

In contrast, B cell-directed superantigens target the B cell compartment. By definition, these agents (1) stimulate a high frequency of B cells, (2) target B cells that have restricted usage of VH or VL family genes, and (3) bind to immunoglobulins outside the sites that bind conventional antigens. A B-cell superantigen that has received considerable attention is staphylococcal SpA (Silverman et al., 2000; Graille et al., 2000). This agent has the ability to bind to the Fc fragment of IgG. This binding has been localized to a region contains α-helical 1 and 2 (helix I and II) structures on each of four or five homologous regions that comprise the extracellular domain of SpA (FIG. 2). However, it is now clear that SpA repeat IgG binding domains contain a second site, located in a region containing helix II and helix III, (FIG. 2) that binds to determinants on the Fab regions of certain immunoglobulins independently of their heavy-chain isotype (Graille et al., 2000). In humans, this so-called alternative site appears to bind only to immunoglobulins that utilize heavy-chain genes of the VH3 subfamily. The x-ray structure of this interaction has been solved, explaining the basis for this interaction (FIG. 3). In the mouse this type of binding is restricted to immunoglobulins using heavy chains belonging to the S107 and J606 VH families.

A number of microbial immunoglobulin binding proteins (IgBP) can bind to regions of immunoglobulin outside the Fc region. Examples of such proteins include SpA, which is also able to bind to the Fab region of Most VH3 sequences. This binding uses a separate binding site to that used for Fc binding. The ability to bind to Fab sequences enables SpA to act as a B cell superantigen. The L protein from the surface of bacterial species Peptostreptococcus magnus was found to bind Ig through L chain interaction, from which the name was suggested (Bjorck, 1988). Unlike SpA and Protein G, which bind to the Fc region of immunoglobulins (antibodies), Protein L binds antibodies through light chain interactions. Since no part of the heavy chain is involved in the binding interaction, Protein L binds a wider range of antibody classes than SpA or G. Protein L binds to representatives of all antibody classes, including IgG, IgM, IgA, IgE and IgD. Single chain variable fragments (ScFv) and Fab fragments also bind to Protein L.

Despite this wide binding range, Protein L is not a universal antibody-binding protein. Protein L binding is restricted to those antibodies that contain kappa light chains. In humans and mice, most antibody molecules contain kappa (κ) light chains and the remainder have lambda (I) light chains. Protein L is only effective in binding certain subtypes of kappa light chains. For example, it binds human VκI, VκIII and VκIV subtypes but does not bind the VκII subtype. Binding of mouse immunoglobulins is restricted to those having VκI light chains (Nilson et al., 1993).

Adhesion Proteins.

Many bacteria must first bind to host cell surfaces. Many bacterial and host molecules that are involved in the adhesion of bacteria to host cells have been identified. Often, the host cell receptors for bacteria are essential proteins for other functions. Members of the MSCRAMM (microbial surface component recognizing adhesive matrix molecule) family of adhesion proteins bind ECM ligands such as collagen, fibronectin, and fibrinogen,

Toxins.

Many virulence factors are proteins made by bacteria that poison host cells and cause tissue damage. For example, there are many food poisoning toxins produced by bacteria that can contaminate human foods. Some of these can remain in “spoiled” food even after cooking and cause illness when the contaminated food is consumed

Enzymes.

A number of virulence factors encode proteases or microbial activators of host protease, which are able to interfere with antibody and complement mediated microbial killing. For example, S. aureus can express a number of proteases or zymogens, and additional virulence factors, which encode enzymes such as lipases, deoxyribonucleases (DNase) and a fatty acid modifying enzymes.

Microbial Antigenic Surface Proteins

Surface proteins of S. aureus are linked to the cell wall by sortase, an enzyme that cleaves polypeptides at a conserved LPXTG motif. SpA, a surface protein of S. aureus synthesized as a precursor bearing an N-terminal signal peptide, which is cleaved during secretion, and a C-terminal sorting signal with an LPXTG motif. After signal peptide-mediated initiation of the precursor into the secretory pathway, the sorting signal directs SpA to the cell wall envelope. The polypeptide is then cleaved between the threonine and the glycine of the LPXTG motif. The liberated carboxyl group of threonine forms an amide bond with the amino group of the pentaglycine crossbridge, thereby tethering the C terminus of SpA to the bacterial peptidoglycan. The genome of S. aureus encodes at least 10 different surface proteins bearing C-terminal sorting signals with an LPXTG motif. Many of these polypeptides are known to interact with various human tissues, serum proteins, or polypeptides of the extracellular matrix. For example, SpA binds to the Fc portion of immunoglobulins, a mechanism that is thought to prevent opsonophagocytosis of staphylococci after their entry into the human host. Binding of the clumping factors, ClfA and ClfB, to fibrinogen promotes bacterial adhesion to vascular and endocardic lesions. The FnbA and FnbB surface proteins bind to fibronectin. This interaction allows staphylococci to adhere to various tissues and, similar to fibronectin-binding proteins of Streptococcus pyrogenes, presumably provides for the invasion and apoptotic death of infected epithelial cells.

According to the embodiments described herein, anti-microbial monoclonal antibodies and variant monoclonal antibodies that have variable domains that recognize one or more microbial cell surface or secreted antigens are provided.

In some embodiments, IgG antibodies, such as a human IgG antibody, a humanized or a chimeric IgG class antibody or their variants are provided. In such embodiments, the antigen recognition region of the antibody is directed against one or more microbial cell surface or secreted antigens (i.e., antigen specific immune binding). In some embodiments, the one or more microbial cell surface or secreted antigens include ClfA, SpA and Sbi.

In other embodiments, IgG antibodies, such as a non-human IgG antibody, or their variants are claimed for use in veterinary medicine. In such embodiments, the antigen recognition region of the antibody is directed against one or more microbial cell surface or secreted antigen.

Virulence Factors of a Target Microbe, S. aureus

In some embodiments, the antibodies and variant antibodies described herein may be designed to target one or more virulence factors produced by the target microbe, which according to some aspects, is S. aureus. S. aureus produces an array of virulence factors (Foster, 2005), examples of which include (1) cell surface proteins that promote colonization of host tissues (e.g. SpA (Protein A), Clumping Factor A (ClfA); (2) invasins that promote bacterial spread in tissues (e.g. leukocidin, hyaluronidase); (3) cell surface factors that inhibit phagocytic engulfment and complement mediated killing (SpA, Sbi, Capsular Polysaccharide Serotypes 5 and 8 (Cps 5 and 8); (4) biochemical properties that enhance their survival in phagocytes (proteases, and protease activators: among the array of secreted staphylococcal factors, a number of proteases, including the serine proteases V8 (SspA/V8) and SpIA-SpIF, the cysteine proteases ScpA (staphopain A) and SspB (staphopain B), the metalloprotease aureolysin and, staphylokinase which can activate host zymogens; (5) immunoglobulin binding proteins (SpA, Sbi, SSL10, SSL7); (6) membrane-damaging toxins that lyse eukaryotic cell membranes (e.g. γ-hemolysins, leukotoxin E-D, Panton-Valentin leukocidin; (7) exotoxins that damage host tissues or otherwise provoke symptoms of disease (e.g. Enterotoxins A, B, C, D, G, H); (8) superantigens which compromise the T cell or B cell response (e.g. SpA, Enterotoxin B, TSST-1, SAC1-3); and (9) inherent and acquired resistance to antimicrobial agents. Several of the virulence factors that may be affected by the variant antibodies described herein are described below.

SpA.

SpA (Protein A), which exists in both secreted and membrane-associated forms, possesses two distinct Ig-binding activities: each domain can bind Fcγ (the constant region of IgG involved in effector functions, as described above) and Fab (the Ig fragment responsible for antigen recognition) (Boyle, 1990). SpA is a 42-kDa protein covalently anchored in the staphylococcal cell wall through its carboxyl terminal end. The protein is comprised of five repeated domains (E, D, A, B, C) of ˜58 residues linked to the cell surface by region Xr, which contains a variable number of short 8-residue repeats (FIG. 2). Each SpA domain can bind with high affinity to the Fc region of immunoglobulin G and to the Fab region of immunoglobulin of the VH3 subclass (Jansson et al., 1998, Moks et al., 1986; Roben et al., 1995; Sasso et al., 1989). The interaction with IgG Fc hinders phagocytosis because bacteria become coated with IgG in an inappropriate conformation not recognized by the Fc receptor on neutrophils. Moreover, SpA-bound IgG cannot stimulate complement fixation by the classical pathway. An additional consequence of the ability of SpA to bind to B lymphocytes displaying IgM bearing VH3 heavy chains is the induction of proliferation resulting in depletion of a significant part of the B cell repertoire (Goodyear et al., 2004; Viau et al., 2005).

Both the SpA-Fc and SpA-Fab interactions have been analyzed at the molecular level with co-crystallized complexes (Deisenhofer 1981; Gouda et al., 1998; Graille et al., 2000). The SpA domains adopt three-helix bundles. One face includes residues from helices I and II binds IgG Fc, whereas residues from helices II and III on the other face bind VH3 Ig (Graille et al., 2000). The residues from helix II that bind Fc are different from those that bind Fab, with the exception of a single glutamine (Gln-32 in SpA domain D) (Deisenhofer 1981; Graille et al., 2000). SpA also binding strongly to a number of other proteins including von Willebrand factor (vWF) (O'Seaghdha et al., 2006), the TNF receptor I (TNFRI) (Gomez et al., 2006), the Epidermal growth factor receptor (EGFR) (Gomez et al., 2007) and also binds to an undefined target on osteoblasts (Claro et al., 2011).

The SpA Fcγ binding site has been localized to the elbow region at the CH2 and CH3 interface of most IgG subclasses, and this binding property has been extensively used for the labeling and purification of antibodies (Deisenhofer, 1981; Tashiro & Montelione, 1995). The X-ray structure of the SpA IgG-binding domains in complex with the Fc region of IgG have been solved and residues from helix I and II that are involved in the interaction have been identified and verified by site-directed mutagenesis, and by the existence of allotypes of IgG3 (with an Arg435 residue) that do not bind SpA. The consequence of the interaction between SpA and IgG-Fc is to coat the surface of the cell with IgG molecules that are in the incorrect orientation to be recognized by Fc receptors on effector cells. This could explain the anti-phagocytic effect of SpA and its role in the pathogenesis of S. aureus infections. Protein-A-deficient mutants of S. aureus are phagocytosed more efficiently by neutrophils in vitro and show decreased virulence in several animal infection models (Gemmell et al., 1997; Palmqvist et al., 2002).

SpA (Protein A) also acts as a B-cell superantigen through interactions with the heavy-chain variable part of Fab fragments, and sequesters immunoglobulins by forming insoluble immune complexes with human IgG. It has been shown that the formation of insoluble immune complexes is mediated by the binding of (VH3+) Fab fragments in addition to Fc. B-cell superantigens, unlike conventional antigens, bind to the Fab regions of immunoglobulin (Ig) molecules outside their complementarity-determining regions (CDRs) reviewed in references (Levinson et al., 1995; Silverman, 1997). These unconventional antigens can react with a substantial amount of a host's peripheral B-cell repertoire and serum Igs by virtue of their ability to interact with many members of an entire variable region heavy (VH) or variable region light (VL) gene family (Levinson & Kozlowski, 1996).

S. aureus SpA (Protein A) is one of the most studied B-cell SAg. Although it had long been known that this microbial product binds to the Fc region of IgG, it became clear that SpA also binds, via an alternative site, to determinants outside the CDRs in the Fab region of Igs. SpA reacts with the Fabs of most VH3 Igs, which are expressed on 30 to 60% of human peripheral B cells. The crystal structure of an S. aureus SpA domain complexed with a Fab fragment of human IgM has been solved, showing the molecular basis for B-Cell receptor recognition and superantigen activity. The interactions of SpA with the Fab region of membrane-anchored Igs can stimulate a large fraction of B cells, contributing to lymphocyte clonal selection. The crystal structure of the complex between domain D of SpA and the Fab fragment of a human IgM antibody to 2.7-Å resolution has been solved (Graille et al., 2000). In the complex, helices II and III of domain D interact with the variable region of the Fab heavy chain (V_(H)) through framework residues, without the involvement of the hypervariable regions implicated in antigen recognition. The contact residues are highly conserved in human V_(H)3 antibodies but not in other families. The contact residues from domain D also are conserved among all SpA Ig-binding domains, suggesting that each could bind in a similar manner. Correlation with antibody sequence usage indicates that the Fab binding specificity is restricted to products of the human variable region of the Fab heavy chain V_(H)3 family that represent nearly half of inherited V_(H) genes (Sasso et al., 1989; Sasso et al., 1991; Sasano et al., 1993; Hillson et al., 1993) and their homologues in other mammalian species (Seppala et al., 1990; Cary et al., 1999). Presumably through interactions with surface membrane-associated V_(H)3-encoded B-cell antigen receptors (Romagnani et al., 1982), in vitro stimulation with SpA can contribute to selection of these B cells and promote their production of antibodies that may include rheumatoid factor autoantibodies (Kristiansen et al., 1994); Kozlowski et al., 1995). In vivo exposure to recombinant SpA can result in supraclonal suppression and deletion of B-lymphocytes that are susceptible based on their V_(H) usage (Silverman et al., 1998; Cary et al., 2000).

Although the mechanism(s) are not defined, experimental models indicate that SpA enhances staphylococcal virulence (Foster et al., 1988; Patel et al., 1987). Many features of the interactions of SpA with host B lymphocytes are akin to those of superantigens for T lymphocytes that cause a variety of inflammatory diseases including toxic shock syndrome, food poisoning, and exfoliative syndromes (Kotzin et al., 1993; Bohach et al., 1990; Papageorgiou et al., 1998) and T-cell superantigens also have been postulated to contribute to the pathogenesis of autoimmune disease (Li et al., 1999). These superantigens target T-cell receptors (TcRs) from particular variable 13 chain (V_(β)) families and induce global changes in T lymphocyte repertoires (Kotzin et al., 1993). The site responsible for Fab binding is structurally separate from the domain surface that mediates Fcγ binding. As first demonstrated in a crystallographic complex and recently reinvestigated in NMR studies the interaction of Fcγ with domain B primarily involves residues in helix I with lesser involvement of helix II (Graille et al., 2000). With the exception of the Gln-32, a minor contact in both complexes, none of the residues that mediate the Fcγ interaction are involved in Fab binding. The area buried in the Fcγ-domain B interface is 1,320 Å², which is comparable to the 1,220 Å² buried in the current complex with Fab. However, the nature of these buried SpA residues differs significantly, as the Fab binding is dominated by polar contacts whereas the Fcγ interaction is predominantly hydrophobic. To examine the spatial relationship between these different Ig-binding sites, the SpA domains in these complexes were superposed (Graille et al., 2000) to construct a model of a complex between a Fab, a SpA domain, and an Fcγ molecule. Fab and Fcγ form a sandwich about opposite faces of the helix II without evidence of steric hindrance of either interaction. These findings illustrate how, despite its small size (i.e., 56-61 aa), SpA domains can simultaneously display both activities, explaining experimental evidence that the interactions of Fcγ and Fab with an individual domain are noncompetitive (Starovasnik et al., 1999).

SpA has also been found to activates tumor necrosis factor receptor 1 (TNFR1) (Gomez et al., 2004) Staphylococci frequently cause pneumonia, and these clinical isolates often have increased expression of SpA, suggesting that this protein may have a role in virulence. It has been found that TNFR1, a receptor for tumor-necrosis factor-α (TNF-α) that is widely distributed on the airway epithelium, is a receptor for SpA (Gomez et al., 2004).

SpA can also act directly as an immune effector itself through its ability to bind and activate tumor necrosis factor α (TNF-α) receptor 1 (TNFR1) (Gomez et al., 2004, 2006). This interaction is particularly important at sites of infection where TNF-α signaling is important, as in the lung. SpA-TNFR1 interaction is essential for the pathogenesis of pneumonia as TNFR1 null mice are not susceptible to S. aureus pneumonia and SpA-defective mutants of S. aureus do not cause infection in wild-type animals. SpA activates proinflammatory signaling through binding to TNFR1 and activation of TRAF2, the p38/c-Jun NH2-terminal kinase MAPKs, and NF-κB (Gomez et al., 2004). TNFR1 ectodomain shedding is induced by SpA (Gomez et al., 2004), presumably by activating the TNF-converting enzyme (TACE or ADAM17) through a signaling pathway not yet elucidated. As there is no apparent homology between the trimeric TNFR1 and IgG, both of which function as receptors for SpA, we were interested in defining the molecular basis for the SpA-TNFR1 interaction.

Each SpA binding domain includes a triple helical bundle (Deisenhofer 1981). By analyzing a series of amino acid substitutions in the SpA D domain, Gomez et al (2006) showed that the residues important in the interaction between SpA D and the Fc region of IgG are also involved in binding to and activating TNFR1. SpA residues that are on the opposite face of the protein that are involved in IgM Fab binding are not involved in the interaction with TNFR1 (Gomez et al., 2006). The IgG Fc region binds to residues exposed on the face formed by helices I and II. TNFR-1 also binds to this face but there are some differences in the residues of SpA that are involved. In particular, leucine 17 is crucial for binding to IgG but not for TNFR-1 binding.

SpA is known to bind human von Willebrand factor (VWF), a protein that is essential for haemostasis, with an affinity of 15 nM as measured by surface plasmon resonance using full length recombinant SpA and VWF that had been purified from plasma. This interaction was shown to occur in the presence of physiological IgG concentrations. Heritable defects in VWF result in von Willebrand's disease, a common bleeding disorder, symptoms of which can mirror severe hemophilia. The main function of VWF is to capture platelets by binding to the platelet receptor GPIb-a and immobilize them at the site of damage to a blood vessel and to stimulate the formation of a blood clot. The VWF protein consists of four types of repeat domain A, B, C and D. Domains are arranged in the sequence D′-D3-A1-A2-A3-D4-B1-B2-B3-C1-C2-CK in the mature protein (for review, see Sadler J. E, 1998). The crystal structure of the recombinant A1 domain in complex with platelet glycoprotein Gibe has been solved (Emsley et al., 1998; Huizinga et al., 2002; Uff et al., 2002). Binding of circulating VWF to the ligands such as collagen in exposed subendothelial matrix of damaged blood vessels under high shear-stress stimulates a conformational change which promotes immobilized VWF binding to Gplba on platelets (Siedlecki et al., 1996; Novak et al., 2002; Hulstein et al., 2005). Circulating platelets are captured and activated, stimulating the formation of a thrombus (Kroll et al., 1996; Xiong et al., 2003). The ability of S. aureus to bind VWF could contribute to the adherence of the bacterium to platelets or to damaged blood vessels. By studying a Spa-deficient mutant of S. aureus it was shown that the Spa-VWF interaction is necessary for efficient recruitment of S. aureus by platelets under high shear stress in whole blood (Pawar et al., 2004). Also fluid-shear adhesion experiments suggested that VWF binding to Spa can promote adherence of circulating S. aureus cells to immobilized collagen (Mascara et al., 2003). In a recent study, it was shown that Spa is sufficient for adherence of bacteria to immobilized VWF under low shear conditions. Recombinant Spa and VWF truncates were used to identify and characterize the domain(s) in each protein that are involved in binding and to refined the VWF binding domain in SpA by site-directed mutagenesis (O'Seaghdha et al., 2006).

Previous studies have suggested that the SpA-VWF interaction is important in S. aureus adherence to platelets under conditions of shear stress and that Spa expression is sufficient for adherence of bacteria to immobilized VWF under low fluid shear (Pawar et al., 2004). The full-length recombinant Ig-binding region of SpA, Spa-EDABC, fused to glutathione-S-transferase (GST), bound recombinant VWF in a dose-dependent and saturable fashion with half maximal binding of about 30 nM in immunosorbent assays. Full-length (FL)-Spa did not bind recombinant VWF A3 domain but displayed binding to recombinant VWF domains A1 and D′-D3 (half-maximal binding at 100 nM and 250 nM, respectively). Each recombinant SpA Ig-binding domain bound to the A1 domain in a similar manner to the FL-Spa molecule (half-maximal binding 100 nM). Amino acid substitutions were introduced in the GST-SpaD protein at sites known to be involved in IgG Fc or in VH3-Fab binding. Mutants altered in residues that recognized IgG Fc but not those that recognized VH3 Fab had reduced binding to VWF-A1 and D′-D3. This indicated that both VWF regions recognized a region on helices I and II that overlapped the IgG Fc binding site (O'Seaghdha et al., 2006).

Osteomyelitis is a debilitating infectious disease of the bone. It is predominantly caused by S. aureus and is associated with significant morbidity and mortality. It is characterized by weakened bones associated with progressive bone loss. Currently the mechanism through which either bone loss or bone destruction occurs in osteomyelitis patients is poorly understood (Claro et al., 2011). S. aureus SpA (Protein A) has recently been shown to binds directly to osteoblasts (Claro et al., 2011). This interaction prevents proliferation, induces apoptosis and inhibits mineralization of cultured osteoblasts. Infected osteoblasts also increase the expression of RANKL, an important protein involved in initiating bone desorption. None of these effects was seen in a mutant of S. aureus lacking SpA. Complementing the SpA-defective mutant with a plasmid expressing spa or using purified SpA resulted in attachment to osteoblasts, inhibited proliferation and induced apoptosis to a similar extent as wildtype S. aureus. These events demonstrate mechanisms through which loss of bone formation and bone weakening may occur in osteomyelitis patients.

Staphylococcal SpA is a conserved surface component of all S. aureus strains, consisting of an N-terminal IgG-binding domain, an Xr or short sequence-repeat region (SSR) encoded by variable numbers of 24-bp repeated DNA sequences, and a C-terminal anchor to the bacterial cell wall. Resent studies have shown that the Xr domain of SpA, activates known components of the type I IFN cascade and that this contributes to the virulence of the organism as a respiratory pathogen (Martin et al., 2009).

Sbi.

In addition to SpA, many stains of S. aureus also produce Sbi, a second protein with Fc binding activity. Sbi is a multidomain protein, which was originally identified as an IgG-binding, and 132 glycoprotein-I binding protein (Zhang et al., 1998). Sbi is a 436-amino acid protein that occurs in many S. aureus strains, including methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) strains. From its N terminus, Sbi includes four small domains up to residue 266 followed by eight copies of a PXXXX repeat motif with a high concentration of glutamine, lysine, aspartate, valine, and isoleucine and then a C-terminal tyrosine-rich 130-residue region (FIG. 4). Unlike SpA, Sbi lacks the typical Gram-positive cell wall anchoring sequence LPXTG, but it does have a predicted proline-rich cell wall-spanning segment (Zhang et al., 1998). Evidence from Western blots of fractionated cells from several S. aureus strains, including Newman, indicates that most Sbi is secreted into the medium. It has also been suggested that Sbi is associates with the bacterial surface through electrostatic interactions (Zhang et al., 1998). Sbi has also been shown to bind a plasma component, adhesion protein β2-glycoprotein I (β2-GPI), a protein that has been implicated in blood coagulation (Zhang et al., 1999; Bouma et al., 1999). It has been demonstrated that Sbi interferes directly with the adaptive immune system through its two N-terminal IgG binding domains (Sbi-I and Sbi-II) (Zhang, L, 1998), and also modulates the innate immune system through its third and fourth domains (Sbi-III and Sbi-IV) (Burman et al., 2008). Specifically, Sbi binds complement protein C3 through Sbi-IV interaction with C3 subunits and induces a futile consumption of complement predominantly via fluid phase activation of the alternative pathway. Sbi fragments containing domains (Sbi-E) and III-IV induce this futile consumption of complement, whereas isolated Sbi-IV does not. Sbi-IV is nevertheless strongly inhibitory in an assay measuring alternative pathway activation (Burman et al., 2008).

SSL7 and SSL10.

SSL7 (formerly named SET1) and SSL10 are members of the staphylococcal superantigen-like (SSL) proteins family (Lina et al., 2004; Williams et al., 2000), related to the staphylococcal enterotoxins (SEs) or superantigens. The SSL proteins have 30% sequence identity with toxic shock syndrome 1 (TSST-1) and 25% or less identity with other SEs. Despite the sequence differences, the SSL proteins have a typical SE tertiary structure consisting of a distinct oligonucleotide/oligosaccharide binding (OB-fold) linked to a β-grasp domain (Arcus et al., 2002a; Arcus, 2002b). Similar to the se genes, the ssl genes are located in a pathogenicity island (SaPIn2) and are likely to be significant virulence factors. Most healthy individuals have antibodies to SSL proteins (A1-Shangiti et al., 2005), and the ssl genes exhibit marked allelic variance consistent with selective pressure from the host immune system (Baba et al., 2002). However, unlike SE, the SSL proteins do not have superantigen activity, but some have been shown to inhibit important molecules of the host immune system. SSL10 (Staphylococcus Super antigen like protein 10) bind IgG1 not IgG2/3/4. The dissociation equilibrium constant for the interaction between human IgG and recombinant SSL10 was estimated to be 220 nM. Recombinant SSL10 inhibited the binding of complement component C1q to IgG. The binding site of SSL10 to IgG1 has been located by site directed mutagenesis to residues within the CH2 domain. Specifically, mutation of IgG1 at residues 274 and 276 to the residues found in IgG3 (which does not bind SSL 10) abolish binding to the variant IgG1 (Patel et al., 2010). In contrast to SSL10, SSL7 bind to the Fc domain interface in human IgA.

Antibody Structure and Interactions with Immunoglobulin Binding Proteins

Antibodies are immunological proteins that bind a specific antigen. In most mammals, including humans and mice, antibodies are constructed from paired heavy and light polypeptide chains. Each chain is made up of individual immunoglobulin (Ig) domains, and thus the generic term immunoglobulin is used for such proteins. Each chain is made up of two distinct regions, referred to as the variable and constant regions. The light and heavy chain variable regions show significant sequence diversity between antibodies, and are responsible for binding the target antigen. The constant regions show less sequence diversity, and are responsible for binding a number of natural proteins to elicit important biochemical events. In humans there are five different classes of antibodies including IgA (which includes subclasses IgA1 and IgA2), IgD, IgE, IgG (which includes subclasses IgG1, IgG2, IgG3, and IgG4), and IgM. The distinguishing features between these antibody classes are their constant regions, although subtler differences may exist in the Variable or V region. FIG. 1 shows an IgG antibody, used here as an example to describe the general structural features of immunoglobulins. IgG antibodies are tetrameric proteins that include two heavy chains and two light chains. Each IgG heavy chain includes four immunoglobulin domains linked from N- to C-terminus in the following order: heavy chain variable domain (VH), heavy chain constant domain 1 (CH1), heavy chain constant domain 2 (CH2), and heavy chain constant domain 3 (CH3) (VH-CH1-CH2-CH3; also referred to as VH-Cγ1-Cγ2-Cγ3, referring to the heavy chain variable domain, constant gamma I domain, constant gamma 2 domain, and constant gamma 3 domain respectively). The CH1-CH2-CH3 or Cγ1-Cγ2-Cγ3 domains are also referred to collectively as the heavy chain constant region. The IgG light chain is composed of two immunoglobulin domains linked from N- to C-terminus in the following order light chain variable domain (VL) and light chain constant domain (CL) (VL-CL).

Each variable region of an antibody (VH and VL) contains the antigen binding determinants of the molecule, and thus determines the specificity of an antibody for its target antigen. The variable region is so named because it is the most distinct in sequence from other antibodies within the same class. The majority of sequence variability occurs in the complementarity determining regions (CDRs). There are 6 CDRs total, three in each variable domain (VH and VL), designated VH CDRI, VH CDR2, VH CDR3, VL CDRI, VL CDR2, and VL CDR3. The variable region outside of the CDRs is referred to as the framework (FR) region. Although not as diverse as the CDRs, sequence variability does occur in the FR region between different antibodies. Overall, this characteristic architecture of antibodies provides a stable scaffold (the FR region) upon which substantial antigen binding diversity (the CDRs) can be explored by the immune system to obtain specificity for a broad array of antigens.

A number of high-resolution structures are available for a variety of variable region fragments from different organisms, some unbound and some in complex with antigen. The sequence and structural features of antibody variable regions are well characterized (Morea et al., 1997; Morea et al., 2000), and the conserved features of antibodies have enabled the development of a wealth of antibody engineering techniques (Maynard et al., 2000). For example, it is possible to graft the CDRs from one antibody, for example a murine antibody, onto the framework region of another antibody, for example a human antibody. This process, referred to in the art as “humanization,” enables generation of antibody therapeutics that have a lower immunogenicity as compared to nonhuman antibodies. Fragments including the variable region can exist in the absence of other regions of the antibody, including for example, the antigen binding fragment (Fab) which includes VH-CH1 and VH-CL, the variable fragment (Fv) which includes VH and Vu, the single chain variable fragment (scFv) which includes VH and VL linked together in the same chain, as well as a variety of other variable region fragments (Little et al., 2000).

Part of the heavy chain constant region is referred to as the Fc domain or region. The Fc region of an antibody interacts with a number of Fc receptors and ligands, imparting an array of important functional capabilities referred to as effector functions. For IgG the Fc region, as shown in FIG. 1, includes Ig domains CH2 and CH3 and the N-terminal hinge leading into CH2. An important family of Fc receptors for the IgG class is the Fc gamma receptors (FcγRs). These receptors mediate communication between antibodies and the cellular arm of the immune system (Raghavan et al., 1996; Ravetch et al., 2001). In humans this protein family includes Fcγ RI (CD64), including isoforms FcγRIa, FcγRIb, and FcγRIc; FcγRII (CD32), including isoforms FcγRIIa (including allotypes H131 and R13I), Fcγ RIIb (including Fcγ RIIb-1 and FcγRIIb-2), and FcγRIIc; and FcγRIII (CD16), including isoforms FcγRIIa (including allotypes VI58 and F158) and FcγRIIIb (including allotypes Fcγ RIIIb-NAI and Fcγ RIIIbNA2) (Jefferis et al., 2002). These receptors typically have an extracellular domain that mediates binding to Fc, a membrane spanning region, and an intracellular domain that may mediate some signaling event within the cell. These receptors are expressed in a variety of immune cells including monocytes, macrophages, neutrophils, dendritic cells, eosinophils, mast cells, platelets, B cells, large granular lymphocytes, Langerhans' cells, natural killer (NK) cells, and γγ T cells.

Formation of the Fc/FcγR complex recruits these effector cells to sites of bound antigen, typically resulting in signaling events within the cells and important subsequent immune responses such as release of inflammation mediators, B cell activation, endocytosis, phagocytosis, and cytotoxic attack. The ability to mediate cytotoxic and phagocytic effector functions is a potential mechanism by which antibodies destroy targeted cells. The cell-mediated reaction wherein nonspecific cytotoxic cells that express FcγRs recognize bound antibody on a target cell and subsequently cause lysis of the target cell is referred to as antibody dependent cell-mediated cytotoxicity (ADCC) (Raghavan et al., 1996; Ghetie et al., 2000; Ravetch et al., 2001). The cell-mediated reaction wherein nonspecific cytotoxic cells that express FcγRs recognize bound antibody on a target cell and subsequently cause phagocytosis of the target cell is referred to as antibody dependent cell-mediated phagocytosis (ADCP). In the case of antimicrobial activity, the cell mediated anti-microbial reaction is generally referred to as opsono phagocytosis. Opsonization involves the binding of an opsonin, e.g., antibody, to a receptor on the pathogen's cell membrane. After opsonin binds to the membrane, phagocytes are attracted to the pathogen. The Fab portion of the antibody binds to the antigen, whereas the Fc portion of the antibody binds to an Fc receptor on the phagocyte, facilitating phagocytosis. The receptor-opsonin complex can also create byproducts like C3b and C4b which are important components of the complement system. These components are deposited on the cell surface of the pathogen and aid in its destruction. A number of structures have been solved of the extracellular domains of human FcγRs, including FcγRIIa (protein data bank (pdb) accession code IH9V) (Sondermann et al., 2001) (pdb accession code IFCG) (Maxwell et al., 1999), FcγRIIb (pdb accession code 2FCB) (Sondermann et al., 1999) and FcγRIIIb (pdb accession code IE4J) (Sondermann et al., 2000). All FcγRs bind the same region on Fc, at the N-terminal end of the Cγ2 domain and the preceding hinge. This interaction is well characterized structurally (Sondermann et al., 2001), and several structures of the human Fc bound to the extracellular domain of human FcγRIIIb have been solved (pdb accession code IE4K) (Sondermann et al., 2000), (pdb accession codes HIS and IIIX) (Radaev et al., 2001), as well as has the structure of the human IgE Fc/FcERIa complex (pdb accession code IF6A) (Garman et al., 2000).

The different IgG subclasses have different affinities for the FcγRs, with IgG1 and IgG3 typically binding substantially better to the receptors than IgG2 and IgG4 (Jefferis et al., 2002). All FcγRs bind the same region on IgG Fc, yet with different affinities: the high affinity binder FcγRI has a Kd for IgG1 of 10⁻⁸ M whereas the low affinity receptors FcγRII and FcγRIII generally bind at 10⁻⁶ M and 10⁻⁵ M, respectively. The extracellular domains of FcγRIIa and FcγRIIIb are 96% identical; however FcγRIIIb does not have an intracellular signaling domain. Furthermore, whereas FcγRI, FcγRIIa/c, and FcγRIIIa are positive regulators of immune complex-triggered activation, characterized by having an intracellular domain that has an immunoreceptor tyrosine-based activation motif (ITAM), FcγRIIb has an immunoreceptor tyrosine-based inhibition motif (ITIM) and is therefore inhibitory. Thus the former are referred to as activation receptors, and FcγRIIb is referred to as an inhibitory receptor. An overlapping but separate site on Fc, serves as the interface for the complement protein Clq. Antibodies can also destroy pathogens or cancerous cells by complement-dependent cytotoxicity (CDC) whereby antibodies bound to the cell-surface initiate deposition and activation of early complement components. In the same way that Fc/FcγR binding mediates opsonophagocytosis, ADCC and ADCP, Fc/Clq binding mediates complement dependent cytotoxicity (CDC) or complement deposition on the target cell surface. Clq forms a complex with the serine proteases Clr and Cls to form the Cl complex. Clq is capable of binding six antibodies, although binding to two IgGs is sufficient to activate the complement cascade. Similar to Fc interaction with FcγRs, different IgG subclasses have different affinity for Clq, with IgG1 and IgG3 typically binding substantially better to the FcγRs than IgG2 and IgG4 (Jefferis et al., 2002). There is currently no structure available for the Fc/Clq complex; however, mutagenesis studies have mapped the binding site on human IgG for Clq to a region involving residues D270, K322, K326, P329, and P331, and E333 (Idusogie et al., 2000; Idusogie et al., 2001).

A site on Fc between the CH2 and CH3 domains of IgG, mediates interaction with the neonatal receptor FcRn, the binding of which recycles endocytosed antibody from the endosome back to the bloodstream (Raghavan et al., 1996; Ghetie et al., 2000). This process, coupled with preclusion of kidney filtration due to the large size of the full-length molecule, results in favorable antibody serum half-lives ranging from one to three weeks. Binding of Fc to FcRn also plays an important role in antibody transport.

The binding site for FcRn on Fc overlaps with the site at which S. aureus SpA, streptococcal Protein G and a variety of other microbial Fc Binding Proteins (FcBP) bind. The tight binding by these proteins has been exploited as a means to purify antibodies by employing SpA or Protein G affinity chromatography during protein purification. Thus, the fidelity of this region on Fc is important for both the clinical properties of antibodies and their purification. Available structures of the rat Fc/FcRn complex (Martin et al., 2001), and of the complexes of Fc with Proteins A and G (Deisenhofer, 1981; Sauer-Eriksson et al., 1995; Tashiro et al., 1995) provide insight into the interaction of Fc with these proteins. An important feature of the Fc region is the conserved N-linked glycosylation that occurs at N297, shown in FIG. 1. This carbohydrate, or oligosaccharide as it is sometimes referred, plays an important structural and functional role for the antibody, and is one of the principle reasons that antibodies must be produced using mammalian expression systems. While not wanting to be limited to one theory, it is believed that the structural purpose of this carbohydrate may be to stabilize or solubilize Fc, determine a specific angle or level of flexibility between the Cγ3 and Cγ2 domains, keep the two Cγ2 domains from aggregating with one another across the central axis, or a combination of these. Efficient Fc binding to FcγR and Clq requires this modification and alterations in the composition of the N297 carbohydrate or its elimination affect binding to these proteins (Umaiia et al., 1999; Davies et al., 2001; Mimura et al., 2001; Radaev et al., 2001; Shields et al., 2001; Shields et al., 2002; Simmons et al., 2002). Yet the carbohydrate makes little if any specific contact with FcγRs (Radaev et al., 2001), indicating that the functional role of the N297 carbohydrate in mediating Fc/Fcγ R binding may be via the structural role it plays in determining the Fc conformation. This is supported by a collection of crystal structures of four different Fc glycoforms, which show that the composition of the oligosaccharide impacts the conformation of Cγ2 and as a result the Fc/Fcγ R interface (Krapp et al., 2003).

The features of antibodies discussed above,—specificity for its target, ability to mediate immune effector functions, and good half-lifes in serum-make antibodies powerful therapeutics. Monoclonal antibodies are used therapeutically for the treatment of a variety of conditions including cancer, inflammation, cardiovascular disease and infectious diseases. There are currently several antibody products on the market and hundreds in development. In addition to antibodies, an antibody-like protein that is finding an expanding role in research and therapy is the Fc fusion (Chamow et al., 1996; Ashkenazi et al., 1997). An Fc fusion is a protein wherein one or more polypeptides are operably linked to Fc. An Fc fusion combines the Fc region of an antibody, and thus its favorable effector function and pharmacokinetics, with the target-binding region of a receptor, ligand, or some other protein or protein domain. The role of the latter is to mediate target recognition, and thus it is functionally analogous to the antibody variable region. Because of the structural and functional overlap of Fc fusions with antibodies, the discussion on antibodies herein is also applicable to Fc fusions.

The mechanisms by which an antibody neutralizes pathogenic material can be diverse, including antibody dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis, complement-dependent cytotoxicity (CDC), opsonization, and steric hindrance, almost all of which require the antibody Fc region to interact with cellular receptors (Marasco & Sui, 2007; Lehner 1989; Lazar et al. 2006). For instance, ADCC depends upon the Fc interaction with the activating FcγRIIIa receptor, present on natural killer cells and other leukocytes. Increasing the affinity and selectivity of this interaction through three Fc amino acid substitutions increased ADCC by two orders of magnitude in vitro (Lazar et al., U.S. Patent Publication No. 20080242845). Additionally, heavy chain constant region variants with increased ability to recruit complement have been described. Variants demonstrated enhanced potency in a cell-based CDC assay and improved binding affinity to C1q. (Moore et al., 2010)

Antibodies have been used to bind and inactivate pathogenic material for many years, originally being isolated as polyclonal antibody mixtures from immunized horse serum. This “passive immunotherapy” was used successfully to treat many viral and bacterial infections but due to numerous problems, including product heterogeneity and low specific titer, coupled with risks of immunogenicity and viral contamination, lost favor after the introduction of antibiotics (Casadevall et al., 2004).

The emergence of antibiotic-resistant microorganisms, emerging viruses and the threat of engineered microorganisms coupled with advances in understanding pathogenic mechanisms and antibody technology leaves this class of therapeutics poised for a comeback (Casadevall et al., 2004; Zeitlin et al., 2000). Antibodies are attractive anti-infective therapeutics for their ability to recognize pathogen-associated ligand molecules with exquisite specificity and to recruit additional immune system components such as complement and natural killer cells, facilitating pathogen inactivation and removal. When properly designed, an antibody can effectively eliminate or control the infection. Unfortunately, efforts to develop recombinant monoclonal antibodies that recapitulate polyclonal anti-sera has not been straightforward, largely due to challenges in identifying appropriate target epitopes, microbial evasion of the humeral immune response and interactions with the rest of the immune system. In the cases of RSV and anthrax, important neutralizing epitopes have been identified, resulting in a remarkably successful drug in the first case and several promising candidates in the second. Several approaches to treating infection involve antibodies that directly bind surface-exposed or associated molecules on whole pathogen cells. These antibodies (depending on the isotype selected) can act by (1) recruiting immune system components to eliminate the pathogen through antibody effector functionalities (e.g., complement, CDC, ADCC, ADCP and opsonophagocytosis); (2) blocking cell associated pathogenic mechanisms, i.e., type III secretion of virulence factors; and (3) directly killing pathogens by targeted delivery of chemotherapeutic agents. These approaches are less developed than those for antiviral or anti-toxin therapies in that none have been approved for use and several promising candidates for treatment of Staphylococcus infections reached Phase III trials, only to miss their efficacy targets.

Variant Immunoglobulins Having Attenuated Binding to Virulence Factors

According to the embodiments described herein, variant antibodies having attenuated non-immune binding to one or more IgBP virulence factors are provided. In some embodiments, the antibodies have a variant heavy chain constant region (i.e., a variant CH1-CH2-CH3 domain or variant Cγ1-Cγ2-Cγ3 domain) having attenuated binding to one or more microbial immunoglobulin binding proteins (IgBPs).

According to the embodiments described herein, the disclosure provides anti-microbial monoclonal immunoglobulins, such as variant IgG immunoglobulins, in which at least one amino acid from the IgG heavy chain constant region is substituted with another amino acid which is different from that present in the parent antibody. The amino acid substitution or substitutions may be in any one or more of the heavy chain constant domains, CH1, CH2 or CH3.

In some embodiments, the monoclonal antibody is a mammalian, chimeric, humanized of human anti-microbial IgG variant antibody in which at least one amino acid from an IgG heavy chain constant region, is substituted with at least one amino acid that differs from that present in the parent antibody. Such variant anti-microbial antibodies have attenuated Fc binding to one or more microbial Fc Binding proteins or Fc binding protein domains expressed by the target microbe.

In other embodiments, the monoclonal antibody is a animal anti-microbial Ig variant antibody for veterinary use, in which at least one amino acid from the IgG heavy chain constant region is substituted with another amino acid which is different from that present in the parent antibody. Such variant anti-microbial antibodies have attenuated Fc binding to one or more microbial Fc Binding proteins or Fc binding protein domains expressed by the target microbe.

The variant immunoglobulin IgG heavy chain and light chain constant regions described herein can be combined with immunoglobulin variable heavy and light chain regions (the variable domain), which bind antigens produced by microbes that express one or more microbial immunoglobulin binding protein.

In some embodiments, the variable domain of the antibody binds to a microbial protein that is a microbial immunoglobulin binding protein, and the heavy chain constant regions of the antibody is a variant IgG Fc which has attenuated binding to one or more microbial Ig Binding Protein or Fc Binding Protein domain expressed by the target microbe.

In other embodiments, the variable domain of the antibody binds to a microbial protein that is not an microbial immunoglobulin binding protein, and the heavy chain constant region of the antibody is a variant IgG Fc which has attenuated binding to one or more microbial Ig Binding Proteins or Fc Binding Protein domains expressed by the target microbe.

The heavy chain constant region variant IgG immunoglobulins claimed herein have enhanced antimicrobial activity relative to their parental antibodies.

In some embodiments such variant IgG heavy chain constant polypeptide sequences are combined with immunoglobulin heavy chain variable polypeptide sequences and light chains polypeptide sequences, which bind one or more cell surface or secreted microbial antigen.

In some embodiments, immunoglobulins with variant heavy chain constant regions having altered (i.e., decreased) non-immune binding to one or more microbial IgBP are provided. The embodiments described herein provide modified antibodies having altered non-immune IgBP binding relative to the corresponding unmodified antibody. More particularly, the embodiments described herein are directed to variant human or humanized monoclonal antibodies directed against microbial surface antigens or surface associated antigens, which have attenuated Fc binding to one or more microbial IgBPs.

The embodiments described herein are directed to variant IgG immunoglobulin heavy chain constant region-containing polypeptides that have attenuated heavy chain constant regions binding to one or more microbial IgBPs as a consequence of the introduction of amino acid changes within the immunoglobulin heavy chain region.

According to the embodiments described herein, the variant anti-microbial antibodies of the disclosure may include one or more sequences derived from at least 4 regions of the IgG antibody. These regions include, but are not limited to:

-   -   The heavy chain constant region, which includes domains CH1, the         hinge region, CH2 and CH3. This region of the antibody is         responsible for the effector function of the antibody. In some         embodiments, this region is derived from human IgG1. In         alternative embodiments, the Fc region is of mixed isotype in         which the CH3 domain of IgG1, or the CH2 and CH3 domains of         IgG1, are exchanged with their homologous domains from IgG3 of         any human allotype. The EU numbering of the heavy chain constant         region corresponds to approximate positions of H118-H446     -   The heavy chain variable domain, which contains the antigen         recognition region of the heavy chain, including the CDR1, CDR2         and CDR3 and framework regions. This region can be derived from         a human antibody, from a chimeric or humanized antibody, or by         humanization of a non-human antibody.     -   The light chain constant regions: In one embodiment, the light         chain constant region is a kappa light chain. In other         embodiments the light chain constant region is a lambda light         chain. The EU numbering positions for a light chain correspond         to approximate positions of L108-L214     -   The light chain variable domain, which includes the antigen         recognition region of the light chain, including the CDR1, CDR2         and CDR3 and framework regions. This region can be derived from         a human antibody, from a chimeric or humanized antibody, or by         humanization of a non-human antibody.

In some embodiments, the heavy chain constant region variant antibody is of IgG immunoglobulin, in which at least one amino acid from the heavy chain constant region selected from, but not limited to amino acid residues (i.e., EU positions) 214, 251, 252, 253, 254, 274, 276, 311, 314, 356, 358, 380, 382, 384, 419, 422, 428, 431, 432, 433, 434, 435, 436 and 438 is substituted with an amino acid residue different from that present in the unmodified IgG1 antibody. The substitutions described herein are not limiting and in some aspect, additional substitution residues may be made. Further, at least one amino acid from the heavy chain constant region may be a single amino acid substitution alone, or a combination of at least two amino acids selected from any combination of one or more of the amino acid substitutions described herein, combined with one or more second amino acid substitution describe herein, or alternatively, may be combined with another substitution not disclosed herein. Substitutions, either alone or in combinations, attenuates the binding of one or more microbial Ig Binding Protein to the heavy chain constant region of the variant antibody

In some embodiments, the heavy chain constant region variant antibody is of isotype IgG1, in which at least one amino acid from the heavy chain constant region selected from, but not limited to amino acid residues (i.e., EU positions) 214, 251, 252, 253, 254, 274, 276, 311, 314, 356, 358, 380, 382, 384, 419, 422, 428, 431, 432, 433, 434, 435, 436 and 438 is substituted with an amino acid residue different from that present in the unmodified IgG1 antibody. The substitutions described herein are not limiting and in some aspect, additional substitution residues may be made. Further, at least one amino acid from the heavy chain constant region may be a single amino acid substitution alone, or a combination of at least two amino acids selected from any combination of one or more of the amino acid substitutions described herein, combined with one or more second amino acid substitution describe herein, or alternatively, may be combined with another substitution not disclosed herein. Substitutions, either alone or in combinations, attenuates the binding of one or more microbial Ig Binding Protein to the heavy chain constant region of the variant antibody

In embodiments in which the heavy chain constant region variant anti-microbial antibody is directed against S. aureus, amino acid changes can be introduced into the heavy chain constant CH2 domain to attenuate SSL10 binding to the variant immunoglobulin. Separate mutations can be introduced into the CH2 or CH3 domain to attenuate Sbi and/or SpA binding to the Fc domain. Mutations can also be introduced into the heavy chain variable FW region to attenuate superantigen type SpA binding to the Fab domain of VH3 derived antibodies.

In some embodiments, amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg, resulting in attenuated binding of the Fc domain of the variant antibody to Sbi and/or SpA (Including but not limited to SEQ ID: 31-46).

In some embodiments, amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg and amino acid residue (i.e., EU position) 274 from the heavy chain constant region is substituted with Gln resulting in attenuated binding of the Fc domain of the variant antibody to Sbi and SSL 10 or SpA (Including but not limited to SEQ ID: 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56)

In some embodiments, amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg and amino acid residue (i.e., EU position) 436 from the heavy chain constant region is substituted with Phe resulting in attenuated binding of the Fc domain of the variant antibody to Sbi and/or SpA (Including but not limited to SEQ ID: 39-46).

In some embodiments, amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg, amino acid residue (i.e., EU position) 436 from the heavy chain constant region is substituted with Phe and amino acid residue (i.e., EU position) 274 from the heavy chain constant region is substituted with Gln resulting in attenuated binding of the Fc domain of the variant antibody to Sbi and SSL 10 and/or SpA (Including but not limited to SEQ ID: 40, 42, 44, 46)

In some embodiments, amino acid residue (i.e., EU position) 422 from the heavy chain constant region is substituted with Ile and amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg resulting in attenuated binding of the variant antibody to Sbi and/or SpA (Including but not limited to SEQ ID 33, 34, 37, 38, 41, 42, 45, 46).

In some embodiments, amino acid residue (i.e., EU position) 422 from the heavy chain constant region is substituted with Ile, amino acid residue (i.e., EU position) 274 from the heavy chain constant region is substituted with Gln and amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg resulting in attenuated binding of the variant antibody to Sbi and SSL 10 and/or SpA (Including but not limited to SEQ ID 34, 38, 42, 46).

In some embodiments, amino acid residue (i.e., EU position) 422 from the heavy chain constant region is substituted with Ile, amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg and amino acid residue (i.e., EU position) 436 from the heavy chain constant region is substituted with Phe resulting in attenuated binding of the variant antibody to Sbi and/or SpA (Including but not limited to SEQ ID: 41, 42, 45, 46).

In some embodiments, amino acid residue (i.e., EU position) 422 from the heavy chain constant region is substituted with Ile, amino acid residue (i.e., EU position) 274 from the heavy chain constant region is substituted with Gln, amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg and amino acid residue (i.e., EU position) 436 from the heavy chain constant region is substituted with Phe resulting in attenuated binding of the variant antibody to Sbi and/or SpA (Including but not limited to SEQ ID:42, 46).

In some embodiments, amino acid residue (i.e., EU position) 419 from the heavy chain constant region is substituted with Glu and amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg resulting in attenuated binding of the variant antibody to Sbi and/or SpA (Including but not limited to SEQ ID: 35-38, 43-46)

In some embodiments, amino acid residue (i.e., EU position) 419 from the heavy chain constant region is substituted with Glu, amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg and amino acid residue (i.e., EU position) 274 from the heavy chain constant region is substituted with Gln resulting in attenuated binding of the variant antibody to Sbi and SSL10 and/or SpA (Including but not limited to SEQ ID: 36, 38 44, 46).

In some embodiments, amino acid residue (i.e., EU position) 419 from the heavy chain constant region is substituted with Glu, amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg and amino acid residue (i.e., EU position) 436 from the heavy chain constant region is substituted with Phe, resulting in attenuated binding of the variant antibody to Sbi and/or SpA (Including but not limited to SEQ ID: 43-46).

In some embodiments, amino acid residue (i.e., EU position) 419 from the heavy chain constant region is substituted with Glu, amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg, amino acid residue (i.e., EU position) 274 from the heavy chain constant region is substituted with Gln and amino acid residue (i.e., EU position) 436 from the heavy chain constant region is substituted with Phe, resulting in attenuated binding of the variant antibody to Sbi and/or SpA (Including but not limited to SEQ ID: 44, 46).

In some embodiments, amino acid residue (i.e., EU position) 419 from the heavy chain constant region is substituted with Glu, amino acid residue (i.e., EU position) 422 from the heavy chain constant region is substituted with Ile and amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg resulting in attenuated binding of the variant antibody to Sbi and/or SpA (Including but not limited to SEQ ID: 37, 38, 45, 46).

In some embodiments, amino acid residue (i.e., EU position) 419 from the heavy chain constant region is substituted with Glu, amino acid residue (i.e., EU position) 422 from the heavy chain constant region is substituted with Ile, amino acid residue (i.e., EU position) 274 from the heavy chain constant region is substituted with Gln and amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg resulting in attenuated binding of the variant antibody to Sbi and SSL10 and/or SpA (Including but not limited to SEQ ID: 38, 46).

In some embodiments, amino acid residue (i.e., EU position) 419 from the heavy chain constant region is substituted with Glu, amino acid residue (i.e., EU position) 422 from the heavy chain constant region is substituted with Ile, amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg and amino acid residue (i.e., EU position) 436 from the heavy chain constant region is substituted with Phe, resulting in attenuated binding of the variant antibody to Sbi and/or SpA (Including but not limited to SEQ ID: 45, 46).

In some embodiments, amino acid residue (i.e., EU position) 419 from the heavy chain constant region is substituted with Glu, amino acid residue (i.e., EU position) 422 from the heavy chain constant region is substituted with Ile, amino acid residue (i.e., EU position) 435 from the heavy chain constant region is substituted with Arg, amino acid residue (i.e., EU position) 274 from the heavy chain constant region is substituted with Gln and amino acid residue (i.e., EU position) 436 from the heavy chain constant region is substituted with Phe, resulting in attenuated binding of the variant antibody to Sbi and SSL10 and/or SpA (Including but not limited to SEQ ID: 46).

In some embodiments, amino acid residue (i.e., EU position) 436 from the heavy chain constant region is substituted with Phe resulting in attenuated binding of the Fc domain of the variant antibody to Sbi and/or SpA (Including but not limited to SEQ ID: 39-48, 53-56).

In some embodiments, amino acid residue (i.e., EU position) 436 from the heavy chain constant region is substituted with Phe and amino acid residue (i.e., EU position) 274 from the heavy chain constant region is substituted with Gln resulting in attenuated binding of the Fc domain of the variant antibody to Sbi and SSL 10 and/or SpA (Including but not limited to SEQ ID: 40, 42, 44, 46, 48, 54, 56).

In some embodiments, amino acid residue (i.e., EU position) 254 from the heavy chain constant region is substituted with Thr resulting in attenuated binding of the variant antibody to Sbi and/or SpA (Including but not limited to SEQ ID: 49-56).

In some embodiments, amino acid residue (i.e., EU position) 254 from the heavy chain constant region is substituted with Thr and amino acid residue (i.e., EU position) 274 from the heavy chain constant region is substituted with Gln resulting in attenuated binding of the variant antibody to Sbi and SSL10 and/or SpA (Including but not limited to SEQ ID: 50, 52, 54, 56).

In some embodiments, amino acid residue (i.e., EU position) 252 and 254 from the heavy chain constant region are substituted with Thr resulting in attenuated binding of the variant antibody to Sbi and/or SpA (Including but not limited to SEQ ID: 51, 52, 55, 56)

In some embodiments, amino acid residue (i.e., EU position) 252 and 254 from the heavy chain constant region are substituted with Thr, and amino acid residue (i.e., EU position) 274 from the heavy chain constant region is substituted with Gln resulting in attenuated binding of the variant antibody to Sbi and SSL10 and/or SpA (Including but not limited to SEQ ID: 52, 56)

In some embodiments, amino acid residue (i.e., EU position) 254 from the heavy chain constant region is substituted with Thr and amino acid residue (i.e., EU position) 456 from the heavy chain constant region is substituted with Phe resulting in attenuated binding of the variant antibody to Sbi and/or SpA (Including but not limited to SEQ ID: 53-56).

In some embodiments, amino acid residue (i.e., EU position) 254 from the heavy chain constant region is substituted with Thr, amino acid residue (i.e., EU position) 274 from the heavy chain constant region is substituted with Gln and amino acid residue (i.e., EU position) 456 from the heavy chain constant region is substituted with Phe resulting in attenuated binding of the variant antibody to SSL10 and Sbi and/or SpA (Including but not limited to SEQ ID: 54, 56).

In some embodiments, amino acid residue (i.e., EU position) 252 and 254 from the heavy chain constant region are substituted with Thr and amino acid residue (i.e., EU position) 456 from the heavy chain constant region is substituted with Phe resulting in attenuated binding of the variant antibody to Sbi and/or SpA (Including but not limited to SEQ ID: 55, 56).

In some embodiments, amino acid residue (i.e., EU position) 252 and 254 from the heavy chain constant region are substituted with Thr, amino acid residue (i.e., EU position) 456 from the heavy chain constant region is substituted with Phe and amino acid residue (i.e., EU position) 274 from the heavy chain constant region is substituted with Gln resulting in attenuated binding of the variant antibody to Sbi and SSL10 and/or SpA (Including but not limited to SEQ ID: 56).

In some embodiments, amino acid residue (i.e., EU position) 274 and/or 276 from the heavy chain constant region are substituted with another amino acid, which is different from that present in an unmodified parental antibody. The resulting variant antibody variant antibody has attenuated binding to the SSL10 IgBPs compared with the unmodified antibody.

In some embodiments, amino acid residue (i.e., EU position) 274 from the heavy chain constant region is substituted with Gln, which is different from that present in an unmodified parental antibody. The resulting variant antibody has attenuated binding to SSL10 IgBPs compared with the unmodified antibody (Including but not limited to SEQ ID: 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56).

In some embodiments, amino acid residue (i.e., EU position) 276 from the heavy chain constant region is substituted with Lys, which is different from that present in an unmodified parental antibody. The resulting variant antibody has attenuated binding to SSL10 IgBPs compared with the unmodified antibody.

In some embodiments, amino acid residue (i.e., EU position) 274 and 276 from the heavy chain constant region is substituted with Gln and Lys respectively, which is different from the residues present in an unmodified parental antibody. The resulting variant antibody has attenuated binding affinity for SSL10 IgBPs compared with the unmodified antibody.

In some embodiments, where the immunoglobulin is directed against a staphylococcal antigen, a variant IgG1 antibody having attenuated binding to S. aureus SSL 10 as compared with the parental antibody is provided, wherein either one of both of amino acid residues (i.e., EU position) 274 and 276 from the heavy chain constant region are substituted with Gln and Lys respectively.

In some embodiments, antibodies having a heavy chain constant region substantially identical to a naturally occurring class IgG1 antibody constant region are provided, wherein at least two amino acid residue selected from residues (i.e., EU positions) 214, 251, 252, 253, 254, 274, 276, 311, 314, 356, 358, 380, 382, 384, 419, 422, 428, 431, 432, 433, 434, 435, 436 and 438 are different from that present in the parental antibody, thereby attenuating binding of the variant heavy chain constant region (relative to the parental antibody) to one or more FcBP selected from the list: S. aureus SSL10, Sbi and Protein.

In some embodiments, antibodies having a heavy chain constant region substantially identical to a naturally occurring class IgG1 antibody heavy chain constant region are provided, wherein at least three amino acid residue selected from residues (i.e., EU positions) 214, 251, 252, 253, 254, 274, 276, 311, 314, 356, 358, 380, 382, 384, 419, 422, 428, 431, 432, 433, 434, 435, 436 and 438 are different from that present in the naturally occurring class IgG1 antibody, thereby attenuating binding of the variant heavy chain constant region (relative to the parental antibody) to one or more FcBP selected from the list: S. aureus SSL10, Sbi and Protein.

In some embodiments, antibodies having a heavy chain constant region substantially identical to a naturally occurring class IgG1 antibody heavy chain constant region are provided, wherein at least three amino acid residue selected from residues (i.e., EU positions) 274, 276, 419, 422, 435 and 436 are different from that present in the naturally occurring class IgG1 antibody, thereby attenuating binding of the variant heavy chain constant region (relative to the parental antibody) to one or more FcBP selected from the list: S. aureus SSL10, Sbi and Protein.

In some embodiments, antibodies having a heavy chain constant region substantially identical to a naturally occurring class IgG1 antibody constant region are provided, wherein at least three amino acid residue selected from residues (i.e., EU positions) 214, 252, 254, 274, 276, 356, 358, 419, 422, 431, 435 and 436 are different from that present in the parental antibody, thereby attenuating binding of the variant heavy chain constant region (relative to the parental antibody) to one or more FcBP selected from the list: S. aureus SSL10, Sbi and Protein.

In some embodiments, allotypic versions of variant IgG1 antibodies with attenuated microbial FcBP binding to the variant Fc domain of the antibody are provided, wherein at least one heavy chain amino acid residue selected from residues (i.e., EU positions) 214, 356, 358 and 431 of the heavy chain are different from that present in the parental antibody.

In some embodiments, iso-allotypic versions of variant IgG1 antibodies with attenuated FcBP binding to the variant heavy chain constant region of the antibody are claimed, wherein at least one heavy chain amino acid residue selected from residues (i.e., EU positions) 214, 251, 252, 253, 254, 274, 276, 311, 314, 356, 358, 380, 382, 384, 419, 422, 428, 431, 432, 433, 434, 435, 436 and 438 of the heavy chain are different from that present in the parental antibody.

In some embodiments, iso-allotypic version of variant IgG1 antibodies with attenuated microbial FcBP binding to the variant heavy chain constant region of the antibody are claimed, wherein at least one heavy chain amino acid residue selected from residues (i.e., EU positions) 214, 251, 252, 253, 254, 274, 276, 311, 314, 356, 358, 380, 382, 384, 419, 422, 428, 431, 432, 433, 434, 435, 436 and 438 of the heavy chain are different from that present in the parental antibody. In embodiments amino acid 365 is Glu, 358 is Met, 431 is Ala and 214 is Lys.

In some embodiments, the heavy chain constant region of the variant IgG1 antibody has decreased binding to one or more microbial FcBPs selected from the list including, but not limited to S. aureus Sbi, SpA and SSL10 compared with the parental antibody, in which at least two heavy chain constant region amino acids selected from residues (i.e., EU positions) 214, 251, 252, 253, 254, 274, 276, 311, 314, 356, 358, 380, 382, 384, 419, 422, 428, 431, 432, 433, 434, 435, 436 and 438 are substituted with amino acid residues different from that present in the parental IgG1 antibody.

In some embodiments the heavy chain constant region of the variant IgG1 antibody has decreased binding to one or more microbial FcBPs selected from the group including, but not limited to S. aureus Sbi, SpA and SSL10 compared with the parental antibody, in which at least three heavy chain constant region amino acids selected from residues (i.e., EU positions) 214, 251, 252, 253, 254, 274, 276, 311, 314, 356, 358, 380, 382, 384, 419, 422, 428, 431, 432, 433, 434, 435, 436 and 438 are substituted with amino acid residues different from that present in the parental IgG1 antibody.

In some embodiments, the heavy chain constant region of the antibody, or variant antibody, contains a heavy chain constant region of isotype G1m17.

In some embodiments, the heavy chain constant region of the antibody, or variant antibody, contains a heavy chain constant region of isotype G1m17 that includes an amino acid sequences selected from the group heavy chain constant region 1-27 (SEQ ID NO:30-56).

In other embodiments, the heavy chain constant region of the antibody, or variant antibody, may be substantially encoded by any allotype or isoallotype of any immunoglobulin gene. In one embodiment, the heavy chain constant region variants comprise IgG1 sequences that are classified as Glm(1), Glm(2), Glm(3), Glm(17), nGlm(I), nGlm(2), and/or nGlm(17). Thus, in the context of an IgG1 isotype, the heavy chain constant region variants may comprise a Lys (Glm(17)) or Arg (Glm(3)) at position 214, an Asp356/Leu358 (Glm(1)) or Glu356/Met358 (nGlm(1), and/or a Gly (Glm(2)) or Ala (nGlm(2)) at position 431.

In an alternative embodiment, the antibody variant has a constant heavy chain region of mixed isotype, created by substituting the CH2 and CH3 domains of the parental IgG1 heavy chain constant region with the CH2 and CH3 domains from the IgG3 heavy chain contain region. In some embodiments, the IgG3 heavy chain sequences can be from IgG3 allotypes G3m5,10,11,13,14, G3m5,6,10,11,14, G3m5,6,11,24 or G3m21,28.

In an alternative embodiment, the antibody variant has a constant heavy chain region of mixed isotype, created by substituting the CH3 domains of the parental IgG1 heavy chain constant region with the CH3 domains from IgG3 heavy chain contain region. In some embodiments, the IgG3 heavy chain sequences can be from IgG3 allotypes G3m5,10,11,13,14, G3m5,6,10,11,14, G3m5,6,11,24 or G3m21,28.

In some embodiments, the variant antibodies are of mixed isotype, wherein the IgG1/IgG3 fusion junction is located between amino acid residues (i.e., EU position) 236 and 237.

In some embodiments, the variant antibodies are of mixed isotype, wherein the IgG1/IgG3 fusion junction is located between amino acid residues (i.e., EU position) 340 and 341.

In some embodiments, variant antibodies of mixed isotype having the IgG1/IgG3 fusion junction located between amino acid residues (i.e., EU position) 236 and 237, have one or more amino acid from the mixed isotype heavy chain constant region selected from amino acid residues (i.e., EU position) 214, 251, 252, 253, 254, 274, 276, 311, 314, 356, 358, 380, 382, 384, 419, 422, 428, 431, 432, 433, 434, 435, 436 and 438 that is substituted with an amino acid residue different from that present in the parental mixed isotype antibody.

In some embodiments, variant antibodies of mixed isotype having the IgG1/IgG3 fusion junction located between amino acid residues (i.e., EU position) 340 and 341, have one or more amino acid from the mixed isotype heavy chain constant region selected from amino acid residues (i.e., EU position) 214, 251, 252, 253, 254, 274, 276, 311, 314, 356, 358, 380, 382, 384, 419, 422, 428, 431, 432, 433, 434, 435, 436 and 438, that is substituted with an amino acid residue different from that present in the parental mixed isotype antibody.

In some embodiments, the antibodies described herein may have a variant heavy chain variable region having attenuated non-immune binding to one or more S. aureus superantigens such that the antibody has low or no superantigen type binding to SpA. Such immunoglobulins and their variants can be selected so as to avoid the use of human VH3 derived sequences, which can interact with SpA at a site distinct from the Fc binding site. Alternatively, if VH3 derived sequences are used, and Fab-SpA superantigen type binding is present in the parental immunoglobulin, then modified variable heavy chains are provided in which at least one amino acid from the heavy chain variable region is substituted with an amino acid residue different from that present in the unmodified parental antibody selected from the list of VH residues including but not limited to H15, H17, H19, H57, H59, H64, H65, H66, H68, H70, H81 and H82 (including H82a and other H82 positions) numbered according to Kabat. In some aspects, VH region variants may reduce or abolish the superantigen type binding of the Fab region of said variant antibody to S. aureus SpA relative to the parental antibody, but do not significantly attenuate antigen binding to the antigen binding site of the variant antibody.

In certain embodiments, the antibody has a variant Fab region that attenuates non-immune binding to an S. aureus superantigen such as SpA, and also has one or more heavy chain constant region substitutions that attenuate Fc binding with one or more S. aureus FcBPs. In such embodiments, the antimicrobial antibody, or variant antibody, contains a heavy chain constant region selected from heavy chain constant regions 1-27 (SEQ ID NO: 30-56), and a heavy chain variable domain in which at least one amino acid selected from the list of VH3 residues including H15, H17, H19, H57, H59, H64, H65, H66, H68, H70, H81 and H82 (including H82a and other H82 positions according to Kabat numbering) is substituted with an amino acid residues different from that present in the parental IgG1 antibody.

In some embodiments, the antimicrobial variant IgG1 heavy chain is paired with a kappa light chain of allotype selected from the group Km1, Km2, Km3.

In some embodiments, the antimicrobial variant IgG1 heavy chain is paired with a lambda light chain.

In some embodiments, the antimicrobial variant IgG1 heavy chain is paired with a kappa light chain having either amino acid Val or Ala at position 153 and/or either Leu or Val at amino acid 191 (EU numbering).

To compare the effect of variant heavy chain constant region changes on the binding and effector properties of anti microbial IgG immunoglobulins, control antibodies including parental IgG immunoglobulins and a humanized anti RSV antibody having a matched variant heavy chain constant region are produced and tested. Such controls are important in distinguishing antigen binding by the variable domain of the antibody from heavy chain constant region binding to the target microbial antigen or microbe.

Additional Embodiments of Claimed Heavy Chain Constant Region Variant Immunoglobulins

In some embodiments, the variant immunoglobulins of the present disclosure have enhanced antimicrobial effector function. According to the embodiments described herein, the enhanced anti-microbial effector function, may include, but is not limited to, C1q binding, C3b deposition, ADCC, ADCP, CDC, opsonophagocytic activity, antimicrobial activity, or a combination thereof.

In some embodiments, the variant immunoglobulins of the present disclosure may have altered microbial FcBP and FcRn binding to the heavy chain constant region, without significantly altering other antibody effector functions such as C1q binding or Fc gamma receptor binding to the variant Fc domain.

The heavy chain constant region variant immunoglobulins of the present disclosure may be combined with other Fc modifications known in the art (e.g. Shields el al., J. Biol. Chem, 2001, 276, 6591-6604; Dall'Acqua et al., THE JOURNAL OF BIOLOGICAL CHEMISTRY VOL. 281, NO. 33, pp. 23514-23524, Aug. 18, 2006; reviewed in Natsume et al., Drug Design, Development and Therapy 2009:3 7-16, which are hereby incorporated by reference as if fully set forth herein). The embodiments described herein encompass combining an immunoglobulin or variant thereof, such as those described herein, with other known constant domain modifications to provide additive, synergistic, or novel properties to the modified antibody. The modifications known in the art may enhance the phenotype (anti-microbial activity) of the immunoglobulin or variant immunoglobulins with which they are combined. For example, an IgG Fc domain variant described herein with reduced Fc binding to S. aureus SpA, SSL 10 or Sbi may be combined with one or more heavy chain constant region mutations known to result in C1q binding with higher affinity than a comparable wild type constant region. Such claimed embodiments results in enhanced antimicrobial effector function.

Additionally, mutation or alternations to the hinge region of the variant heavy chain constant region, which enhances stability or the variant immunoglobulin with respect to microbial protease cleavage, are also claimed. Examples of such microbial proteases include but are not limited to IdeS, GluV8 and SpeB.

Some embodiments described herein also relate to modified variant IgG immunoglobulins that have decreased in vivo half-life by virtue of the presence of a modified human IgG1 heavy chain constant region, wherein the IgG heavy chain constant region, or fragment thereof, is modified by the introduction of one or more amino acid changes. The one or more amino acid changes may be an amino acid substitution, or by the engineering of a mixed isotype IgG constant domains, all of which have decreased affinity for one or more microbial FcBP and for the human FcRn receptor.

In some embodiments, modified variant class IgG1 antibodies are provided, wherein the in vivo half-lives are reduced by changes in one or more amino acid residues at positions which have been identified to be involved, either directly or indirectly, in the interaction of the IgG1 with the FcRn receptor. The altered half-life resulting from reduced FcRn binding will decrease the half-life of the modified variant IgG1 relative to a parental IgG1 molecule. This altered half-life will allow better control of patient exposure in the clinic.

In further embodiments, methods for modifying an antibody of class IgG1 or mixed isotype are provided, wherein said method includes substituting at least one amino acid from the heavy chain constant region with an amino acid which is different from that present in an unmodified parent antibody, thereby causing an alteration in the binding affinity of the Fc domain for a microbial FcPB and/or one or more of the following properties: effector function, FcRn binding, serum half-life, stability and/or immunogenicity.

The embodiments described herein further provide for a method of modifying an antibody of class IgG1 wherein said method includes substituting at least one amino acid from the heavy chain constant region selected from amino acid residues (i.e., EU positions) 214, 251, 252, 253, 254, 274, 276, 311, 314, 356, 358, 380, 382, 384, 419, 422, 428, 431, 432, 433, 434, 435, 436 and 438, thereby causing an alteration in the binding affinity for a microbial FcPB and/or one or more of the following properties: effector function. Additionally, present disclosure further provides for a method of producing an antibody variant having a heavy chain constant region of mixed isotype, created by substituting regions of the IgG1 heavy chain constant region with sequences from the IgG3 heavy chain constant region, or a variant IgG including a heavy chain constant region of mixed isotype. Such antibodies and their variants may also contain further modifications, in which at least one amino acid from the heavy chain constant region is substituted with an amino acid residue different from that present in the IgG1, IgG3 or mixed isotope heavy chain parental antibody. The method may include, but is not limited to steps of (a) preparing an expression vector (e.g., a replicable expression vector) that includes a suitable promoter operably linked to DNA encoding at least a constant region of an immunoglobulin heavy chain or a variant thereof, wherein at least one amino acid from the heavy chain constant region is substituted with an amino acid which is different from that present in an unmodified antibody thereby causing an alteration in FcBP binding affinity and/or one or more of the following properties: effector function, FcRn binding, serum half-life, stability, and/or immunogenicity antibodies; (b) transforming host cells with said vector; and (c) culturing said transformed host cells to produce said modified antibody. Optionally, such a method may further include preparing a second expression vector (e.g., a replicable expression vector) that includes a promoter operably linked to DNA encoding a complementary immunoglobulin light chain and further transforming said cell line with said second vector.

The embodiments described herein also include pharmaceutical compositions and methods of prophylaxis and therapy using antibodies and their variants, including modified immunoglobulins (including immunoglobulins conjugated with antimicrobial compound or radionuclides). Also included are methods of diagnosis using modified immunoglobulins and their variants. In some embodiments, the amino acid modifications of the present disclosure may be used to enhance the antimicrobial activity of the therapeutic or prophylactic antibody.

Anti-Microbial Immunoglobulins and their Heavy Chain Constant Region Variants.

According to the embodiments described herein, anti-microbial monoclonal antibodies and their variants are provided. Such anti-microbial monoclonal antibodies and their variants have variable domains which recognize one or more microbial cell surface or secreted antigens.

In some embodiments, IgG antibodies, such as a human IgG antibody, a humanized or a chimeric IgG class antibody or their variants are claimed. In such embodiments, the antigen recognition region of the antibody is directed against one or more microbial cell surface or secreted antigens.

The variant immunoglobulin IgG heavy chain constant region described herein may be combined with one or more immunoglobulin variable heavy and/or light chain regions which bind antigens produced by microbes that express one or more microbial immunoglobulin binding protein.

In some embodiments, the variable domain of the antibody binds to a microbial protein that is a microbial immunoglobulin binding protein, and the heavy chain constant region of the antibody is a variant IgG which has attenuated binding to one or more microbial Ig Binding Protein or Ig Binding Protein domain expressed by the target microbe.

In other embodiments, the variable domain of the antibody binds to a microbial protein that is not an microbial immunoglobulin binding protein, and the heavy chain constant region of the antibody is a variant IgG which has attenuated binding to one or more microbial Ig Binding Proteins or Ig Binding Protein domains expressed by the target microbe.

The anti-microbial heavy chain constant region variants IgG immunoglobulins claimed herein have enhanced antimicrobial activity relative to their parental antibodies.

In some embodiments human, humanized or chimeric anti-microbial heavy chain constant region variant immunoglobulins are claimed, which includes a heavy chain constant region amino acid sequence selected from SEQ ID NO: 31-56.

Anti-S. aureus Immunoglobulins and their Heavy Chain Constant Region Variants.

S. aureus, an important human pathogen for which there is an urgent unmet therapeutic need, a number of microbial immunoglobulin binding proteins may be expressed, including SpA, Sbi, SSL7 and SSL10.

In some embodiments, the target microbe is S. aureus, and variant IgG antibodies may be designed to have attenuated binding to one or more S. aureus IgBPs due to the introduction of one or more amino acid substitutions in the heavy chain constant region relative to the parental IgG.

In other embodiments, the target microbe is S. aureus, and variant antibody heavy chain constant region polypeptide sequences are combined with immunoglobulin heavy chain variable polypeptide sequences and light chains polypeptide sequences, which bind one or more cell surface or secreted S. aureus antigen.

In some embodiments, the S. aureus antigen recognized by the variable domain of immunoglobulins and there variants are cell surface or secreted antigens selected from the list which includes but is not limited to: ClfA, ClfB, Cna, Eap, Ebh, EbpS, FnBPAK, FnBPB, IsaA, IsaB, IsdA, IsdB, IsdH, SasB, SasC, SasD, SasF, SasG, SasH, SasK, SdrC, SdrD, SdrE, Spa, SraP, Coa, Ecb, Efb, Emp, EsaC, EsxA, EssC, FLIPr, FLIPr like, Sbi, SCIN-B, SCIN-C, VWbp, SpA, LTA, CP5, CP8, PNAG, dPNAG, CHIPS, PVL leukocidin, α, β and γ-hemolysins, SAK, Sea, Sep, Seb, Epa, Efb, SCIN, Exfoliatins ETB and ETA, Staphylococcal Enterotoxins SEA, SEB, SECn, SED, SEG, SHE, and SEI, Toxic-shock syndrome toxin TSST-1, Alpha Toxin, Beta toxin, Delta toxin.

Anti-SpA and Anti-Sbi Immunoglobulins and their Heavy Chain Constant Region Variants

In some embodiments, the antigen recognized by the variable domain of the antibody or its variants is S. aureus SpA. In such embodiments, the microbial antigen recognized by the variable domain of the variant IgG antibody is an epitope found in one or more of the repeat homology IgBP domains of S. aureus SpA (referred to as SpA domains E, D, A, B, and C).

In some embodiments, the antigen recognized by the variable domain of the antibody or its variants is S. aureus Sbi. In such embodiments, the antigen epitope recognized by the variable domain of the antibody or its variants is located in one or more of the Sbi IgBP binding domains I and II.

In some embodiments, the antigen epitope recognized by the variable domain of the antibody or its variants is found in two or more of the repeat IgBP homology domains from SpA or Sbi, selected from the list SpA domains E, D, A, B, and C, and Sbi domains I and II.

In some embodiments, the antigen epitope recognized by the variable domain of the antibody or its variants is found in one or more of the repeat IgBP homology domains from both SpA and Sbi, selected from the list SpA domains E, D, A, B, and C, and Sbi domains I and II.

According to the embodiments described herein, anti-SpA monoclonal antibodies and their variants are provided. Such anti-microbial monoclonal antibodies and their variants, have variable domains which recognize S. aureus SpA.

In some embodiments, IgG antibodies, such as a human IgG antibody, a humanized or a chimeric IgG class antibody and their variants are claimed. In such embodiments, the antigen recognition region of the antibody is directed against S. aureus SpA.

In one embodiment, methods whereby monoclonal antibodies are raised or selected are provided. The disclosure also envisages the construction of chimeric antibodies from murine derived antibodies, humanization of non-human antibodies and affinity maturation of human or humanized antibodies.

In one embodiment, the murine monoclonal antibody SPA27 (described in WO 2008/140487 A2) was used for the construction of chimeric IgG immunoglobulins and their variants. The heavy chain and light chain variable domain amino acid sequence of the chimeric antibodies and their variants are shown in SEQ ID NO: 1 and 6.

In some embodiment, the murine monoclonal antibody SPA27 and its humanized versions described in WO 2008/140487 A2 can be used for the construction of chimeric IgG immunoglobulins and their variants. The heavy chain and light chain variable region amino acid sequence of the chimeric antibodies and their variants are shown SEQ ID NO: 1 and 6.

In other embodiments, anti-SpA antibodies known in the art such as monoclonal antibody 76 (described in U.S. Pat. No. 7,488,807 B2), or monoclonal antibody 107 (described in US patent application US 2010/0047252 A1) can be used for the construction of chimeric, heavy chain constant region variant IgG immunoglobulins.

In other embodiments, anti-SpA antibodies known in the art such as monoclonal antibody 3F6, 5A10 and 3D11 (Kim et al., 2012), can be used for the construction of chimeric, heavy chain constant region variant IgG immunoglobulins.

In other embodiments, human SpA antibodies can be cloned from human B cells obtained from patients recovering from a S. aureus infection, or from Patients immunized with a non-toxogenic SpA vaccine (Kim et al., 2012).

To compare the effect of variant heavy chain constant region changes on the effector properties and antimicrobial activity of variant anti-SpA IgG immunoglobulins, control antibodies including parental anti-SpA IgG immunoglobulins and humanized non-specific antibody having a matched variant heavy chain constant region are produced and tested. In one example an anti-RSV parental antibody (IgG1, allotype Gm17) having a heavy and light chain sequence shown in HC3 (SEQ ID NO: 22) and LC2 (SEQ ID NO: 24) or a matched variant heavy chain constant region antibody of HC4 (SEQ ID NO: 23) and LC2 (SEQ ID NO: 24) were produced and tested.

In some embodiments, chimeric anti-SpA heavy chain constant region variant IgG immunoglobulins can be humanized and affinity matured using a number of established methods, which are known in the art.

In some embodiments, the antigen binding portion of the anti-SpA antibody, or heavy chain constant region variant IgG antibody, contains at least one heavy chain variable region that includes an amino acid sequence selected from the group SEQ ID NO: 1-5 (VH Chimeric and VH1-VH4).

In some embodiments the antigen binding portion of the antibody, or heavy chain constant region variant IgG antibody, contains at least one light chain variable regions that includes an amino acid sequence selected from the group SEQ ID NO 6-18 (VL chimeric and VL1-VL12).

In some embodiments, an anti-SpA antibody or heavy chain constant region variant IgG antibody, or antigen-binding portion thereof that includes a light chain variable region amino acid sequence selected form the group SEQ ID NO: 6-18 (VL chimeric and VL1-VL12), and a heavy chain variable region amino acid sequence selected from SEQ ID NO:1-5 (VH chimeric and VH1-VH4) are provided.

In one embodiment, a chimeric parental IgG1 anti-SpA antibody that includes a heavy chain region acid sequence of SEQ ID NO:19 and a light chain amino acid sequence of SEQ ID NO:21 is provided.

In one embodiment, an example chimeric variant IgG1 anti-SpA antibody that includes a variant heavy chain constant acid sequence of SEQ ID NO:20 and a light chain amino acid sequence of SEQ ID NO:21 is provided.

The embodiments described herein also include affinity matured variant anti-S. aureus antibodies in which a human, humanized, or chimeric variable domain of the antibody are derived from an anti-S. aureus antibody. Such claimed affinity matured variant antibodies have at least one amino acid substitution, deletion or insertion relative to the parental heavy or light chain variable domain sequences.

In some embodiments, the disclosure pertains to an anti-SpA antibody or variant, or antigen-binding portion thereof that includes a light chain variable region amino acid sequence selected form the group SEQ ID NO:6-18 (VL chimeric and VL1-VL12), and a heavy chain variable region amino acid sequence selected from SEQ ID NO:1-5 (VH chimeric and VH1-VH4), in which the antibody variable domain or the heavy and/or light chain has been affinity matured resulting in the introduction of variable region amino acid substitutions, insertions or deletions relative to the parental sequence. Such changes result in improved antibody affinity for its target antigen.

In some embodiments in which the antibody is directed against a S. aureus antigen, the variant immunoglobulins also have low or no superantigen type binding to SpA via the Fab region of the immunoglobulin in addition to one or more heavy chain constant region changes that attenuate Fc iterations with one or more S. aureus FcBPs. Such immunoglobulins and their variants can be selected so as to avoid the use of human VH3 derived sequences, which can interact with SpA at a site distinct from the Fc binding site. Alternatively, if VH3 derived sequences are used, and Fab-SpA superantigen type binding is present in the parental immunoglobulin, then modified variable heavy chains are provided in which at least one amino acid from the heavy chain variable FW region is substituted with an amino acid residue different from that present in the unmodified parental antibody selected from the list of VH residues including but not limited to H19 and H82a. In some aspects, VH region variants reduce or abolish the superantigen type binding of the Fab region of said variant antibody to S. aureus SpA relative to the parental antibody, but do not significantly attenuate antigen binding to the antigen binding site of the variant antibody

In an additional embodiment, the modification of human or humanized VH3 family derived anti-S. aureus IgG variable heavy domain residues are claimed which abrogate superantigen type binding of SpA to anti S. aureus immunoglobulins or their heavy chain constant region variants. In one such embodiment the antigen binding portion of the antibody, or heavy chain constant region variant IgG antibody, contains at least one heavy chain variable region that includes an amino acid sequence selected from the group SEQ ID NO:1-5 (VH Chimeric and VH1-VH4), in which at least one amino acid from the heavy chain variable region is substituted with an amino acid residue different from that present in SEQ ID NO:1-5 (VH Chimeric and VH1-VH4), selected from the list of VH residues (position to Kabat numbering) selected from the list including H15, H17, H19, H57, H59, H64, H65, H66, H68, H70, H81 and H82 (including H82a and other H82 positions).

In an additional embodiment, the modification of human or humanized VH3 family derived anti-S. aureus IgG variable heavy domain residues are claimed which abrogate superantigen type binding of SpA to anti S. aureus immunoglobulins or their heavy chain constant region variants. In one such embodiment the antigen binding portion of the antibody, or heavy chain constant region variant IgG antibody, contains at least one heavy chain variable region that includes an amino acid sequence selected from the group SEQ ID NO:1-5 (VH Chimeric and VH1-VH4), in which at least one amino acid from the heavy chain variable FW region is substituted with an amino acid residue different from that present in SEQ ID NO:1-5 (VH Chimeric and VH1-VH4), selected from the list of VH residues including but not limited to H19 and H82a (Kabat numbering).

In an additional embodiment, the modification of human or humanized VH3 family derived anti-S. aureus IgG variable heavy domain residues are claimed which abrogate superantigen type binding of SpA to anti S. aureus immunoglobulins or their heavy chain constant region variants. In one such embodiment the antigen binding portion of the antibody, or heavy chain constant region variant IgG antibody, contains at least one heavy chain variable region that includes an amino acid sequence selected from the group SEQ ID NO:1-5 (VH Chimeric and VH1-VH4), in which at least one amino acid from the heavy chain variable FW region is substituted with an amino acid residue different from that present in SEQ ID NO:1-5 (VH Chimeric and VH1-VH4), in which Asn 82a (Kabat numbering). is either Ser or Gly.

Variant anti-SpA IgG antibodies of the embodiments described herein have amino acid changes in their heavy chain constant region relative to their parental antibodies. These amino acid substitutions result in the variant immunoglobulin having attenuated heavy chain contain domain binding to one or more microbial immunoglobulin binding protein (IgBP).

In some embodiments, in which the antibody is a variant IgG immunoglobulin, the microbial antigen recognized by the antibody is S. aureus SpA (SpA), and the antibody is a variant IgG in which amino acid substitutions have been introduced into the heavy chain constant region so as to attenuate Fc binding to one or more S. aureus IgBPs, including, but not limited to: S. aureus SpA, Sbi and SSL10.

In some embodiments, anti-SpA variant antibodies described herein block one or more function of the SpA domain to which they bind selected from, but not limited to: IgG Fc binding, VH3 Fab binding, TNFR1 binding, vWF binding, EGFR binding and osteoblast binding.

In some embodiments, the variant Fc domain of the anti-SpA antibody does not bind to SpA or Sbi, but will bind to Protein G. Protein G binding of such heavy chain constant region variant anti-microbial immunoglobulins allows for their purification using Protein G affinity chromatography using method well known in the art. In certain embodiments, the variant antibody may bind, via constant domain non-immune binding to Protein G and/or Protein L, but does not bind SpA or Sbi by interaction with the heavy chain constant domain of the variant antibody.

The disclosure also relates to the prophylactic or therapeutic use of such anti-microbial immunoglobulins and their variants, and their use in combinations with additional antimicrobial chemotherapy or anti-infective agents or in combination with one or more additional antimicrobial immunoglobulins

The embodiments described herein also include pharmaceutical compositions and methods of prophylaxis and therapy using antibodies and their variants, including modified immunoglobulins (including immunoglobulins conjugated with antimicrobial compound or radionuclides). Also included are methods of diagnosis using modified immunoglobulins and their variants. In some embodiments, the amino acid modifications of the present disclosure may be used to enhance the antimicrobial activity of the therapeutic or prophylactic antibody

Anti-ClfA Heavy Chain Constant Region Variant Immunoglobulins

In additional embodiments, the antigen recognized by the variable domain of the claimed heavy chain constant region variant immunoglobulin is S. aureus Clumping factor A (ClfA).

In some embodiments a human, humanized or chimeric anti ClfA heavy chain constant region variant immunoglobulin are claimed.

In some embodiments variant humanized or chimeric anti-ClfA antibodies contain a heavy chain, in which at least one amino acid from the heavy chain constant region selected from, but not limited to amino acid residues (i.e., EU positions) 214, 251, 252, 253, 254, 274, 276, 311, 314, 356, 358, 380, 382, 384, 419, 422, 428, 431, 432, 433, 434, 435, 436 and 438 is substituted with an amino acid residue different from that present in the unmodified IgG1 antibody.

In some embodiments a human, humanized or chimeric anti ClfA heavy chain constant region variant immunoglobulin is claimed, including a heavy chain constant region amino acid sequence selected from, but not limited to, SEQ ID NO: 30-56 (heavy chain constant region H1-27).

In one embodiment the heavy and light chain variable domain sequences of the humanized anti-ClfA heavy chain constant region variant immunoglobulin are derived from Tefibazumab.

In one embodiment the heavy and light chain variable domain sequences of the humanized anti-ClfA parental and variants including a variable light chain amino acid sequence SEQ ID NO:29 (VL 13), and a variable heavy chain region amino acid sequence SEQ ID NO:28 (VH 5) are provided.

In one embodiments, anti-ClfA heavy chain constant region variant antibodies, including a variable light chain amino acid sequence SEQ ID NO:29 (LC 13), a variable heavy chain region amino acid sequence SEQ ID NO:28 (VH5), and a heavy chain constant region including of an amino acid sequences selected from the group SEQ ID 30-56 (heavy chain constant region 1-27) are provided.

In one embodiment, the parental anti-ClfA heavy chain and light chain of sequence shown in SEQ ID NO:25 (HC 5) and SEQ ID NO:27 (LC 3) are provided.

In another embodiment, a variant anti-ClfA heavy chain and light chain of sequence SEQ ID NO:26 (HC 6) and SEQ ID NO:27 (LC 3) are provided.

In another embodiment, the heavy and light chain variables domain sequences of the humanized anti-ClfA variant immunoglobulins, have undergone affinity maturation resulting in at least a 2 fold improvement in its affinity for its antigen.

In another embodiment, an anti-ClfA heavy chain constant region variant IgG immunoglobulin, including a light chain amino acid sequence SEQ ID NO:27 (LC 3), and a variant heavy chain sequence SEQ ID NO:26 (HC6) are provided. Also claimed are affinity matured derivative immunoglobulins having at least one amino acid substitution, deletion or insertion relative to the parental heavy or light chain variable sequences (SEQ ID NO:29 and SEQ ID NO:28). In one aspect, affinity matured variable domain variants have an affinity improvement of at lease 2 fold.

In some embodiments, the anti S. aureus activity of the anti-ClfA heavy chain constant region variant IgG immunoglobulin and their affinity-matured progeny are enhanced relative to their parental antibodies.

In some embodiments, the variant anti ClfA immunoglobulins described herein have an increase in one or more of the following Fc mediated effector functions: C1q binding, C3b deposition, complement deposition, opsonophagocytic activity, ADCC, ADCP, CDC and anti-microbial activity.

Additional Claimed Embodiments

The embodiments described herein also include heavy chain constant region variant anti-S. aureus antibodies in which the human, humanized, or chimeric variable domain, or variable domain CDRs of the antibody are derived from an anti-S. aureus antibodies selected from the list: Pagibaximab (a chimeric anti-LTA antibody; Biosynexus/Medimmune), Tefibazumab (a humanized IgG1 anti-ClfA; Aurexis, Inhibitex), CS-D7 (human anti-IsdB IgG1, Merck), Aurograb (scFv fragment anti ABC transporter; NeuTec), anti-Alpha toxin (Medimmune patent application WO/2012/109285), mAb15E11, a murine antibody recognizing Fibronectin-binding proteins A and B. Povenza et al., 2010).

The embodiments described herein also include affinity matured heavy chain constant variant anti-S. aureus antibodies in which the human, humanized, or chimeric variable domain of the antibody are derived from one or more anti-S. aureus antibodies including, but not limited to: Pagibaximab (a chimeric anti-LTA; Biosynexus/Medimmune; FIG. 37), Tefibazumab (humanized IgG1 anti-ClfA, Inhibitex/BMS), CS-D7 (a humanized anti-IsdB IgG1, Merck; FIG. 36), Aurograb (an scFv fragment anti-ABC transporter; NeuTec), and anti-Alpha toxin (Medimmune patent application WO/2012/109285, which is hereby incorporated by reference as if fully set forth herein). Such claimed affinity matured heavy chain constant region variant antibodies have at least one amino acid substitution, deletion or insertion relative to the parental heavy or light chain variable domain sequences.

The antibodies and antibody variants described herein may be of any suitable antibody structure including, but not limited to, full length antibodies, antibody fragments, monoclonal antibodies, bispecific antibodies, multispecific antibodies, peptibodies, intrabodies, minibodies, domain antibodies, synthetic antibodies (sometimes referred to herein as “antibody mimetics”), chimeric antibodies, humanized antibodies, fully human antibodies, antibody fusions or Fc fusions (sometimes referred to as “antibody conjugates”), and fragments thereof, respectively. In one embodiment, the antibodies include multispecific antibodies, such as bispecific antibodies, also sometimes referred to as “diabodies”. These are antibodies that bind to two (or more) different antigens. Diabodies can be manufactured in a variety of ways known in the art (Holliger & Winter, 1993), e.g., prepared chemically or from hybrid hybridomas.

Further, the antibodies and antibody variants described herein may include one or more modifications, such as a covalent modification. Covalent modifications of antibodies that are included herein, are generally, but not always, done post-translationally. For example, several types of covalent modifications of the antibody are introduced into the molecule by reacting specific amino acid residues of the antibody with an organic derivatizing agent that is capable of reacting with selected side chains or the Nor C-terminal residues.

Another type of covalent modification is glycosylation. In another embodiment, the IgG variants disclosed herein can be modified to include one or more engineered glycoforms. An “engineered glycoform,” as used herein, is a carbohydrate composition that is covalently attached to an IgG, wherein said carbohydrate composition differs chemically from that of a parent IgG.

Another type of covalent modification of the antibody includes linking the antibody to various nonproteinaceous polymers, including, but not limited to, various polyols such as polyethylene glycol, polypropylene glycol or polyoxyalkylenes, in the manner set forth in U.S. Pat. Nos. 4,640,835; 4,496,689; 4,301,144; 4,670,417; 4,791,192 or 4,179,337, which are hereby incorporated by reference in their entirety, as if fully set forth herein. In addition, as is known in the art, amino acid substitutions may be made in various positions within the antibody to facilitate the addition of polymers such as PEG. See for example, U.S. Publication No. 2005/0114037, which is incorporated herein by reference in its entirety.

The Fc variants of provided herein are defined according to the amino acid modifications that compose them. Thus, for example, I332E, or Ile332Glu is an Fc variant with the substitution I332E relative to the parent Fc polypeptide. Likewise, S239D/A330L/1332E defines an Fc variant with the substitutions S239D, A330L, and I332E relative to the parent Fc polypeptide. It is noted that the order in which substitutions are provided is arbitrary, that is to say that, for example, S239D/A330L/11332E is the same Fc variant as S239D/1332E/A330L, and so on. For all positions discussed herein, numbering is according to the EU index or EU numbering scheme (Kabat et al., 1991, Sequences of Proteins of Immunological Interest, 5th Ed., United States Public Health Service, National Institutes of Health, Bethesda, which is hereby incorporated by reference in its entirety as if fully set forth herein). The EU index or EU index as in Kabat or EU numbering scheme refers to the numbering of the EU antibody (Edelman et al., 1969, Proc Natl Acad Sci USA 63:78-85, which is hereby incorporated by reference in its entirety as if fully set forth herein).

Heavy chain constant region variants may be substantially encoded by genes from any organism, such as mammals, including but not limited to humans; rodents including, but not limited to, mice and rats; horses; lagomorpha including, but not limited to, rabbits and hares; camelidae including, but not limited to, camels, llamas, and dromedaries; and non-human primates including, but not limited to, Prosimians, Platyrrhini (New World monkeys), Cercopithecoidea (Old World monkeys), Hominoidea (including those disclosed in U.S., Patent Publication No. 2006/0235208 A1), Gibbons, and Lesser and Great Apes. In one embodiment, the heavy chain constant region variants are substantially human.

The parent heavy chain constant region polypeptide may be an antibody. Parent antibodies may be fully human, obtained for example using transgenic mice (Bruggemann et al., 1997) or human antibody libraries coupled with selection methods (Griffiths et al., 1998). The parent antibody need not be naturally occurring. For example, the parent antibody may be an engineered antibody, including but not limited to chimeric antibodies and humanized antibodies (Clark, 2000). The parent antibody may be an engineered variant of an antibody that is substantially encoded by one or more natural antibody genes. In one embodiment, the parent antibody has been or can be affinity matured, as is known in the art. Alternatively, the antibody has been modified in some other way, for example as described in U.S. patent application Ser. No. 10/339,788, filed on Mar. 3, 2003, hereby entirely incorporated by reference.

The heavy chain constant region or Fc variants described herein may be substantially encoded by immunoglobulin genes belonging to any of the antibody classes. In one embodiment, the heavy chain constant region variants find use in antibodies or Fc fusions that comprise sequences belonging to the IgG class of antibodies, including IgG1, IgG2, IgG3, or IgG4. FIG. 5 provides an alignment of these human IgG sequences. In an alternate embodiment the heavy chain constant region variants find use in antibodies or Fc fusions that comprise sequences belonging to the IgA (including subclasses IgA1 and IgA2), IgD, IgE, IgG, or IgM classes of antibodies. The heavy chain constant region variants described herein may comprise more than one protein chain. That is, the present disclosure may find use in an antibody or Fc fusion that is a monomer or an oligomer, including a homo- or hetero-oligomer.

It is well known that immunoglobulin polymorphisms exist in the human population. Gm polymorphism is determined by the IGHGI, IGHG2 and IGHG3 genes which have alleles encoding allotypic antigenic determinants referred to as Glm, G2m, and G3m allotypes for markers of the human IgG1, IgG2 and IgG3 molecules (no Gm allotypes have been found on the gamma 4 chain). Markers may be classified into ‘allotypes’ and ‘isoallotypes’. These are distinguished on different serological bases dependent upon the strong sequence homologies between isotypes. Allotypes are antigenic determinants specified by allelic forms of the Ig genes. Allotypes represent slight differences in the amino acid sequences of heavy or light chains of different individuals. Even a single amino acid difference can give rise to an allotypic determinant, although in many cases there are several amino acid substitutions that have occurred. Allotypes are sequence differences between alleles of a subclass whereby the antisera recognize only the allelic differences. An isoallotype is an allele in one isotype which produces an epitope which is shared with a nonpolymorphic homologous region of one or more other isotypes and because of this the antisera will react with both the relevant allotypes and the relevant homologous isotypes (Clark, 1997; Gorman & Clark, 1990,).

Allelic forms of human immunoglobulins have been well-characterized (WHO Review of the notation for the allotypic and related markers of human immunoglobulins (J Immunogen 1976, 3: 357-362; WHO Review of the notation for the allotypic and related markers of human immunoglobulins. 1976, Eur. J. Immunol. 6, 599-601; Loghem, 1986, all hereby entirely incorporated by reference). Additionally, other polymorphisms have been characterized (Kim et al., 2001). At present, 18 Gm allotypes are known: Glm (1,2,3,17) or Glm (a, x, f, z), G2m (23) or G2m (n), G3m (5, 6, 10, 11, 13, 14, 15, 16, 21, 24, 26, 27, 28) or G3m (bl, c3, b5, bO, b3, b4, s, t, gl, c5, u, v, g5) (Lefranc, et al., The human IgG subclasses: molecular analysis of structure, function and regulation. Pergamon, Oxford, pp. 43-78 (1990); Lefranc, G. et al., 1979, Hum. Genet. 50, 199-211, both hereby entirely incorporated by reference). Allotypes that are inherited in fixed combinations are called Gm haplotypes.

FIG. 7 shows the allotypes of the gamma I chain of human IgG1 and the gamma 3 chain of human IgG3 showing the positions and the relevant amino acid substitutions (Gorman & Clark, 1990; Jefferis & LeFranc, 2009). For comparison, the amino acids found in the equivalent positions in human IgG2, IgG3 and IgG4 gamma chains are also shown.

The heavy chain constant region or Fc variants described herein may be substantially encoded by any allotype or isoallotype of any immunoglobulin gene. In one embodiment, the heavy chain constant region variants may find use in antibodies or Fc fusions that comprise IgG1 sequences that are classified as Glm(1), Glm(2), Glm(3), Glm(17), nGlm(I), nGlm(2), and/or nGlm(17). Thus, in the context of an IgG1 isotype, the heavy chain constant region variants may comprise a Lys (Glm(17)) or Arg (Glm(3)) at position 214, an Asp356/Leu358 (Glm(1)) or Glu356/Met358 (nGlm(1), and/or a Gly (Glm(2)) or Ala (nGlm(2)) at position 431 (FIG. 6).

In one embodiment, the heavy chain constant region variants described herein are based on human IgG1 sequences, and thus human IgG1 sequences are used as the “base” sequences against which other sequences are compared including, but not limited to, sequences from other organisms, for example, rodent and primate sequences. Heavy chain constant region variants may also comprise sequences from other immunoglobulin isotypes, such as IgG2, IgG3 or IgG4 or from different classes such as IgA, IgE, IgD, IgM, and the like. It is contemplated that, although the heavy chain constant region variants of the embodiments described herein are engineered in the context of one parent IgG, the variants may be engineered in or “transferred” to the context of another, second parent IgG. This is done by determining the “equivalent” or “corresponding” residues and substitutions between the first and second IgG, typically based on sequence or structural homology between the sequences of the first and second IgGs. In order to establish homology, the amino acid sequence of a first IgG outlined herein is directly compared to the sequence of a second IgG. After aligning the sequences, using one or more suitable homology alignment programs known in the art (e.g., using conserved residues as between species), allowing for necessary insertions and deletions in order to maintain alignment (i.e., avoiding the elimination of conserved residues through arbitrary deletion and insertion), the residues equivalent to particular amino acids in the primary sequence of the first heavy chain constant region variant are defined. Alignment of conserved residues should conserve 100% of such residues. However, alignment of greater than 75% or as little as 50% of conserved residues is also adequate to define equivalent residues.

Equivalent residues may also be defined by determining structural homology between a first and second IgG that is at the level of tertiary structure for IgGs whose structures have been determined. In this case, equivalent residues are defined as those for which the atomic coordinates of two or more of the main chain atoms of a particular amino acid residue of the parent or precursor are within about 0.13 nm and about 0.1 nm after alignment. Alignment is achieved after the best model has been oriented and positioned to give the maximum overlap of atomic coordinates of non-hydrogen protein atoms of the proteins. Regardless of how equivalent or corresponding residues are determined, and regardless of the identity of the parent IgG in which the IgGs are made, the heavy chain constant region variants described herein may be engineered into any second parent IgG that has significant sequence or structural homology with the heavy chain constant region variant. Thus, for example, if a variant antibody is generated wherein the parent antibody is human IgG1, by using the methods described above or other methods for determining equivalent residues, the variant antibody may be engineered in another IgG1 parent antibody that binds a different antigen, a human IgG2 parent antibody, a human IgA parent antibody, a horse IgG7 or IgG4 antibody, a mouse IgG2a or IgG2b parent antibody, and the like. Again, as described above, the context of the parent heavy chain constant region variant does not affect the ability to transfer the heavy chain constant region variants of the embodiments described herein to other parent IgGs.

The embodiments described herein provide variant antibodies that are optimized for a variety of therapeutically relevant properties. A heavy chain constant region variant that is engineered or predicted to display one or more optimized properties is herein referred to as an “optimized heavy chain constant region variant.” In some embodiments, properties that may be optimized include, but are not limited to, reduced affinity for one or more microbial IgBP or FcBP. In one embodiment, the variants of the embodiments described herein may possess similar or enhanced affinity for a human activating Fcγ R, Fcγ RI, Fcγ RIIa, Fcγ RIIc, Fcγ RIIIa, and/or FcγRIIIb. In an alternate embodiment, the heavy chain constant region variants may be optimized to possess reduced affinity for the human inhibitory receptor FcγRIIb. These embodiments are anticipated to provide IgG polypeptides with enhanced therapeutic properties in humans—for example, similar or enhanced effector function relative to parental IgG and greater anti-microbial potency due to reduced microbial IgBP binding. In other embodiments, Fc of the embodiments described herein may provide enhanced affinity for one or more FcγRs, and reduced binding to FcRn and microbial IgBPs.

Heavy chain constant region variants of the embodiments described herein may comprise modifications that modulate interaction with Fc ligands other than FcγRs, including but not limited to complement proteins, FcRn, and Fc receptor homologs (FcRHs). FcRHs include but are not limited to FcRHI, FcRH2, FcRH3, FcRH4, FcRH5, and FcRH6 (Davis et al., 2002, Immunol. Reviews 190: 123-136, hereby entirely incorporated by reference).

Modifications to reduce immunogenicity may include modifications that reduce binding of processed peptides derived from the parent sequence to MHC proteins. For example, amino acid modifications may be engineered such that there are no or a minimal number of immune epitopes that are predicted to bind, with high affinity, to any prevalent MHC alleles. Several methods of identifying MHC-binding epitopes in protein sequences are known in the art and may be used to score epitopes in an heavy chain constant region variant of the embodiments described herein. See for example WO 98/52976; WO 02/079232; WO 00/3317; U.S. Ser. No. 09/903,378; U.S. Ser. No. 10/039,170; U.S. Ser. No. 60/222,697; U.S. Ser. No. 10/754,296; PCT WO 01/21823; and PCT WO 02/00165; Mallios, 1999, Bioinformatics 15: 432-439; Mallios, 2001, Bioinformatics 17: 942-948; Sturniolo et al., 1999, Nature Biotech. 17: 555-561; WO 98/59244; WO 02/069232; WO 02/77187; Marshall et al., 1995, J. Immunol. 154: 5927-5933; and Hammer et al., 1994, J. Exp. Med. 180: 2353-2358, all of which are hereby entirely incorporated by reference. Sequence-based information can be used to determine a binding score for a given peptide-MHC interaction (see for example Mallios, 1999, Bioinformatics 15: 432-439; Mallios, 2001, Bioinformatics 17: p942-948; Sturniolo et. al., 1999, Nature Biotech. 17: 555-561, all hereby entirely incorporated by reference).

In accordance with the embodiments described herein, conventional molecular biology, microbiology, and recombinant DNA techniques may be used within the skill of the art. Such techniques are explained fully in the literature. See, e.g., Sambrook et al, “Molecular Cloning: A Laboratory Manual” (1989); “Current Protocols in Molecular Biology” Volumes I-III [Ausubel, R. M., ed. (1994)]; “Cell Biology: A Laboratory Handbook” Volumes I-III [J. E. Celis, ed. (1994))]; “Current Protocols in Immunology” Volumes I-III [Coligan, J. E., ed. (1994)]; “Oligonucleotide Synthesis” (M. J. Gait ed. 1984); “Nucleic Acid Hybridization” [B. D. Hames & S. J. Higgins eds. (1985)]; “Transcription And Translation” [B. D. Hames & S. J. Higgins, eds. (1984)]; “Animal Cell Culture” [R. I. Freshney, ed. (1986)]; “Immobilized Cells And Enzymes” [IRL Press, (1986)]; B. Perbal, “A Practical Guide To Molecular Cloning” (1984); all of which are hereby incorporated by reference, as if fully set forth herein.

Methods of Producing Variant Antibodies

The embodiments described herein provide methods for engineering, producing, and screening variant antibodies. The described methods are not meant to constrain the embodiments described herein to any particular application or theory of operation. Rather, the provided methods are meant to illustrate generally that one or more variant antibodies may be engineered, produced, and screened experimentally to obtain variant antibodies with optimized effector function. A variety of methods are described for designing, producing, and testing antibody and protein variants in U.S. Ser. No. 10/672,280, U.S. Ser. No. 10/822,231, U.S. Ser. No. 11/124,620, and U.S. Ser. No. 11/256,060, all hereby entirely incorporated by reference.

Described herein (see, e.g., Examples 1-4 below) are methods of producing monoclonal antibodies that recognize SpA and/or Sbi, methods for selecting antibodies that cross react with multiple SpA IgBP domains (selected from Domains E, D, A, B, C and Sbi domains I and II), methods of selecting antibodies that cross react with one or more SpA IgG binding domains and/or Sbi domains I and/or II, methods of assaying for antigen binding to SpA or Sbi using variant IgG1 antibodies, having one or more amino acid substitutions in the Fc domain which prevent Fc binding to SpA, Sbi or SSL10.

A variety of protein engineering methods may be used to design variant antibodies with optimized effector function. In one embodiment, a structure-based engineering method may be used, wherein available structural information is used to guide substitutions. An alignment of sequences may be used to guide substitutions at the identified positions. Alternatively, random or semi-random mutagenesis methods may be used to make amino acid modifications at the desired positions.

Methods for production and screening of variant antibodies are well known in the art. General methods for antibody molecular biology, expression, purification, and screening are described in Antibody Engineering, edited by Duebel & Kontermann, Springer-Verlag, Heidelberg, 2001; and Hayhurst & Georgiou, 2001; Maynard & Georgiou, 2000, which are hereby incorporated by reference in their entirety, as if fully set forth herein. Also see the methods described in U.S. Ser. No. 10/672,280, U.S. Ser. No. 10/822,231, U.S. Ser. No. 11/124,620, and U.S. Ser. No. 11/256,060, all of which are hereby entirely incorporated by reference.

In one embodiment, the heavy chain constant region variant sequences are used to create nucleic acids that encode the member sequences, and that may then be cloned into host cells, expressed and assayed, if desired. These practices are carried out using well-known procedures, and a variety of methods that may find use in the embodiments described herein are described in Molecular Cloning-A Laboratory Manual, 3rd Ed. (Maniatis, Cold Spring Harbor Laboratory Press, New York, 2001), Molecular Cloning-A Laboratory Manual, 4th Ed. (Green and Sambrook, Cold Spring Harbor Laboratory Press, New York, 2012), and Current Protocols in Molecular Biology (John Wiley & Sons), both entirely incorporated by reference. The variant antibodies of the embodiments described herein may be produced by culturing a host cell transformed with nucleic acid, such as an expression vector, containing nucleic acid encoding the variant antibodies, under the appropriate conditions to induce or cause expression of the protein. A wide variety of appropriate host cells may be used, including but not limited to mammalian cells, bacteria, insect cells, and yeast. For example, a variety of cell lines that may find use in the embodiments described herein are described in the ATCC cell line catalog, available from the American Type Culture Collection. The methods of introducing exogenous nucleic acid into host cells are well known in the art, and will vary with the host cell used.

Purification of Variant Antibodies

In one embodiment, variant antibodies are purified or isolated after expression. Antibodies may be isolated or purified in a variety of ways known to those skilled in the art. Standard purification methods include chromatographic techniques, electrophoretic, immunological, precipitation, dialysis, filtration, concentration, and chromatofocusing techniques. Purification can often be enabled by a particular fusion partner. For example, proteins may be purified using glutathione resin if a GST fusion is employed, Ni+2 affinity chromatography if a His-tag is employed, or immobilized anti-flag antibody if a flag-tag is used. For general guidance in suitable purification techniques, see Antibody Purification: Principles and Practice, 3rd Ed., Scopes, Springer-Verlag, NY, 1994, which is hereby entirely incorporated by reference.

In one embodiment, immunoglobulins and their variants are purified by affinity chromatography on Protein G, Protein L, SpA or by ion exchange chromatography.

Screening Methods

Variant antibodies may be screened using a variety of methods including, but not limited to, those that use in vitro assays, in vivo and cell-based assays, and selection technologies. Automation and high-throughput screening technologies may be utilized in the screening procedures. Screening may employ the use of a fusion partner or label, for example an immune label, isotopic label, or small molecule label such as a fluorescent or calorimetric dye.

In one embodiment, the functional and/or biophysical properties of variant antibodies are screened in an in vitro assay. In another embodiment, the protein is screened for functionality, for example its ability to bind to a microbial IgBP or FcBP, its binding affinity to its target antigen.

As is known in the art, a subset of screening methods includes those that select for favorable members of a library. The methods are herein referred to as “selection methods”, and these methods find use in the embodiments described herein for screening variant antibodies. When protein libraries are screened using a selection method, only those members of a library that are favorable, that is which meet some selection criteria, are propagated, isolated, and/or observed. A variety of selection methods are known in the art that may find use in the embodiments described herein for screening protein libraries. Other selection methods that may find use in the embodiments described herein include methods that do not rely on display, such as in vivo methods. A subset of selection methods referred to as “directed evolution” methods are those that include the mating or breading of favorable sequences during selection, sometimes with the incorporation of new mutations.

In one embodiment, variant antibodies are screened using one or more cell-based or in vivo assays. For such assays, purified or unpurified proteins are typically added exogenously such that cells are exposed to individual variants or pools of variants belonging to a library. These assays are typically, but not always, based on the function of the immunoglobulin polypeptide; that is, the ability of the immunoglobulin polypeptide to bind to its target microbial antigen and mediate some biochemical event, for example effector function, ligand/receptor binding inhibition, and the like. Such assays often involve monitoring the response of target cells to the IgG, for example cell killing, change in cellular morphology, opsonophagacytosi, complement deposition, antimicrobial activity. For example, such assays may measure the ability of variant antibodies immunoglobulins to elicit antimicrobial antigen binding, microbial killing, and microbial FcBP binding, C1g and C3b deposition, opsonophagocytosis, ADCC, ADCP, or CDC. For some assays additional cells or components, that is in addition to the target cells, may need to be added, for example serum complement, IgG which binds to target microbial FcBPs, or effector cells such as peripheral blood monocytes (PBMCs), NK cells, macrophages, and the like. Such additional cells may be from any organism, such as humans, mice, rat, rabbit, and monkey. Antibodies may cause killing of certain microbes, which express the target antigen, or they may mediate attack on target microbes by immune cells, which have been added to the assay. Methods for monitoring target cell death or viability are known in the art, and include the use of dyes, immunochemical, cytochemical, and radioactive reagents.

The biological properties of the variant antibodies of the embodiments described herein may be characterized in cell, tissue, and whole organism experiments. As is known in the art, drugs are often tested in animals, including but not limited to mice, rats, rabbits, dogs, cats, pigs, and monkeys, in order to measure a drug's efficacy for treatment against a disease or disease model, or to measure a drug's pharmacokinetics, toxicity, and other properties. The animals may be referred to as disease models. Therapeutics are often tested in mice, including but not limited to nude mice, SCID mice, xenograft mice, and transgenic mice (including knock-ins and knock-outs). Such experimentation may provide meaningful data for determination of the potential of the protein to be used as a therapeutic. Any organism, such as mammals, may be used for testing. For example because of their genetic similarity to humans, monkeys can be suitable therapeutic models, and thus may be used to test the efficacy, toxicity, pharmacokinetics, or other property of the IgGs of the embodiments described herein. Tests in humans may be performed to obtain approval as drugs. Thus, the IgGs described in the embodiments herein may be tested in humans to determine their therapeutic efficacy, toxicity, immunogenicity, pharmacokinetics, and/or other clinical properties.

In one embodiment, methods of screening and selecting antimicrobial monoclonal antibodies are provided, the variant heavy chain constant region used for antibody selection is of human isotype IgG1 having a His to Arg substitution at position 435 and a Tyr to Phe substitution at position 436. The variant Fc domain may also be used for antibody selection is of human isotype IgG1 having a His to Arg substitution at position 435. The use of such heavy chain constant region variants is important, as they allow differentiation between antigen specific binding by the antibody from heavy chain constant region mediated binding to one of the following IgBPs, including but nor limited to SpA and Sbi

In an additional embodiment of screening and selecting antimicrobial monoclonal antibodies, the variant heavy chain constant region used for antibody selection is of human isotype IgG1 and has a His to Arg substitution at position 435, a Lys to Gln substitution at position 274 and a Tyr to Phe substitution at position 436. In an additional example the variant Fc domain used for antibody selection is of human isotype IgG1 and has a His to Arg substitution at position 435 and a Lys to Gln substitution at position 274. The uses of such heavy chain constant region variants are important so as to differentiate antigen specific variable domain binding of the antibody from heavy chain constant region mediated binding to one of the following IgBPs, including but nor limited to SpA, SSL10 and Sbi.

Therapeutic Uses of the Variant Antibodies

The variant antibodies of the embodiments described herein may find use in a wide range of products. In one embodiment an variant antibody described in the embodiments herein is a therapeutic, a diagnostic, or a research reagent. The variant may find use in an antibody composition that is monoclonal or polyclonal. In one embodiment, variant antibodies described in the embodiments herein may be used to kill target microbes that bear the target antigen, for example gram-positive bacterial cells. In an alternate embodiment, the variant antibodies are used to block, antagonize, or agonize the target antigen, for example for antagonizing a bacterial secreted virulence factor. In an alternative embodiment, variant antibodies described herein are used to block or antagonize target antigen and kill the target microbe that bear the target antigen.

The anti-microbial variant immunoglobulins described herein, which have enhanced anti-microbial activity relative to their parental antibodies, may be used for the prophylactic or therapeutic treatment of a number of important infectious diseases infections and pathological conditions caused by pathogenic microbes. For example, Staphylococcus and Streptococcus bacterial infections are responsible for several diseases, infections, and conditions, such as localized skin infections, diffuse skin infections (e.g., Impetigo), deep, localized infections, acute infective endocarditis, septicemia, necrotizing pneumonia, toxinoses (e.g., toxic shock syndrome and staphylococcal food poisoning), cystitis, meningitis, scarlet fever, Rheumatic fever, necrotizing fascitis, and pneumonia. Many of these diseases and conditions are a result of an opportunistic infection in a patient who has a compromised immune system (e.g., from chemotherapy or HIV infection) or an open wound or incision site (e.g., acute injuries or post-surgery)

Therefore, in some embodiments, methods for treating a disease, infection, or condition caused by one or more pathogenic microbes include a step of administering a therapeutically effective amount of a pharmaceutical composition that includes a variant antibody that has enhanced antimicrobial effects, such as those described herein. In some aspects, the methods for treating the patient are employed to treat the patient after the onset of the disease, infection or condition. In other aspects, the methods for treating the disease are employed to treat the patient after the onset of the disease, infection or condition as a prophylactic treatment. As such, pharmaceutical composition may include a passive vaccine composition that includes one or more variant antibodies, thereby providing passive immunization to the patient.

A “patient” or “subject” for the purposes of the embodiments described herein includes humans and other animals, e.g., mammals. The term “treatment” as used herein is meant to include therapeutic treatment, as well as prophylactic or suppressive measures for a disease, condition or disorder. Thus, for example, successful administration of a pharmaceutical composition that includes a variant antibody of the embodiments described herein prior to onset of the disease results in “treatment” of the disease. As another example, successful administration of a pharmaceutical composition that includes a variant antibody of the embodiments described herein after clinical manifestation of the disease to combat the symptoms of the disease is considered “treatment” of the disease. “Treatment” also encompasses administration of a pharmaceutical composition that includes a variant of the embodiments described herein after the appearance of the disease in order to eradicate the disease. Successful administration of a pharmaceutical composition that includes a variant of the embodiments described herein after onset and after clinical symptoms have developed, with possible abatement of clinical symptoms and perhaps amelioration of the disease, is considered “treatment” of the disease. Those “in need of treatment” as used herein, include mammals already having the disease or disorder, as well as those prone to having the disease or disorder, including those in which the disease or disorder is to be prevented.

In one embodiment, an variant antibody described herein may be administered alone (i.e., as the only therapeutically active agent in a pharmaceutical composition). In other embodiments, the variant antibody is administered in combination with one or more additional therapies. The term “in combination” or “in combination with” as used herein, means in the course of treating at least one disease or condition in a subject using two or more therapies (e.g., therapeutic agents, drugs, treatment regimens, treatment modalities or a combination thereof), in any order. This includes simultaneous administration (or “co-administration”), administration of a first therapy prior to or after administration of a second therapy, as well as in a temporally spaced order of up to several days apart. Such combination treatment may also include more than a single administration of any one or more therapies. Further, the administration of the two or more therapies may be by the same or different routes of administration.

Examples of additional therapies that may be administered in combination with the variant antibodies described herein include, but are not limited to, (1) chemotherapeutic agents (e.g., alkylating agents, antimetabolites, anti-tumor antibiotics, topoisomerase inhibitors, mitotic inhibitors hormone therapy, targeted therapeutics and immunotherapeutics), biological agents, antibodies or variant antibodies such as those described herein, antibodies unrelated to those described herein, antimicrobial agents, antibiotics (e.g., nafcillin, oxacillin, vancomycin, penicillin, ampicillin, aminoglycoside, clarithromycin, or azithromycin), antiviral agents, anti-infective agents, (2) surgery, radiation therapy, or other treatment modalities that may compromise the immune system, and (3) other suitable therapeutic agents, treatment modalities, that may be used to treat a disease, infection or condition caused by a pathogenic microbe or an underlying disease or condition that is common to patients suffering from a disease, infection or condition caused by a pathogenic microbe (e.g., cancer patients, surgery patients, HIV infected patients. In the case where a patient undergoes a surgical procedure or radiation therapy, the variant antibody may be administered before, during or soon surgery for prophylactic treatment of opportunistic infectecions, such as those caused a pathogenic microbe (e.g., Staphyloccus, Streptococcus).

In some embodiments, pharmaceutical compositions are provided wherein an variant antibody described herein and one or more therapeutically active agents are formulated as part of a composition. Formulations of the variant antibodies of the embodiments described herein are prepared for storage by mixing said IgG having the desired degree of purity with optional pharmaceutically acceptable carriers, excipients or stabilizers (Remington's Pharmaceutical Sciences 16th edition, Osol, A. Ed., 1980, which is hereby incorporated by reference in its entirety, as if fully set forth herein), in the form of lyophilized formulations or aqueous solutions. The formulations to be used for in vivo administration are preferably sterile. This is readily accomplished by filtration through sterile filtration membranes or other methods. The variant antibody and other therapeutically active agents disclosed herein may also be formulated as immunoliposomes, and/or entrapped in microcapsules.

The concentration of the therapeutically active heavy chain constant region variant in the formulation may vary from about 0.001 to 100 weight %. In one embodiment, the concentration of the IgG is in the range of 0.003 to 1.0 molar. In order to treat a patient, a therapeutically effective dose of the variant antibody of the embodiments described herein may be administered to the patient. A “therapeutically effective dose,” as used herein means a dose that produces the effects for which it is administered. The exact dose will depend on the purpose of the treatment, and will be ascertainable by one skilled in the art using known techniques. Dosages may range from 0.001 to 100 mg/kg of body weight or greater, for example 0.1, I, 10, or 50 mg/kg of body weight, with I to 10 mg/kg being a preferred range. As is known in the art, adjustments for protein degradation, systemic versus localized delivery, and rate of new protease synthesis, as well as the age, body weight, general health, sex, diet, time of administration, drug interaction and the severity of the condition may be necessary, and will be ascertainable with routine experimentation by those skilled in the art.

Administration of the pharmaceutical composition that includes a variant antibody of the embodiments described herein, such as those in the form of a sterile aqueous solution, may be done in a variety of ways, including, but not limited to, subcutaneously, intravenously, intranasally, intraotically, transdermally, topically (e.g., gels, salves, lotions, creams, etc.), intraperitoneally, intramuscularly, intrapulmonary (e.g., AERx® inhalable technology commercially available from Aradigm, or Inhance® pulmonary delivery system commercially available from Inhale Therapeutics), vaginally, parenterally, rectally, or intraocularly. In some embodiments, the pharmaceutical composition is administered in any of the above routed using a composition in the form of a sterile aqueous solution.

Definitions

In order that for embodiments be more completely understood, several definitions are set forth below. Such definitions are meant to encompass equivalents and are not meant to be limiting.

The terms “ADCC” or “antibody dependent cell-mediated cytotoxicity,” as used herein, mean a cell-mediated reaction wherein nonspecific cytotoxic cells that express FcγRs recognize bound antibody on a target cell and subsequently cause lysis of the target cell.

The terms “ADCP,” or “antibody dependent cell-mediated phagocytosis,” as used herein, mean a cell-mediated reaction wherein nonspecific cytotoxic cells that express FcγRs recognize bound antibody on a target cell and subsequently cause phagocytosis of the target cell.

The terms “amino acid” and “amino acid identity,” as used herein, mean one of the 20 naturally occurring amino acids or any non-natural analogues that may be present at a specific, defined position. The terms “amino acid residue” or “amino acid,” as used herein, refer to amino acids that are preferably in the “L” isomeric form. However, residues in the “D” isomeric form can be substituted for any L-amino acid residue, as long as the desired fictional property of immunoglobulin-binding is retained by the polypeptide. NH₂ refers to the free amino group present at the amino terminus of a polypeptide. COOH refers to the free carboxyl group present at the carboxyl terminus of a polypeptide. In keeping with standard polypeptide nomenclature, J. Biol. Chem., 243:3552-59 (1969), abbreviations for amino acid residues are shown in the following Table of Correspondence:

TABLE OF CORRESPONDENCE SYMBOL 1-Letter 3-Letter AMINO ACID Y Tyr tyrosine G Gly glycine F Phe phenylalanine M Met methionine A Ala alanine S Ser serine I Ile isoleucine L Leu leucine T Thr threonine V Val valine P Pro proline K Lys lysine H His histidine Q Gln glutamine E Glu glutamic acid W Trp tryptophan R Arg arginine D Asp aspartic acid N Asn asparagine C Cys cysteine

It should be noted that all amino-acid residue sequences are represented herein by formulae whose left and right orientation is in the conventional direction of amino-terminus to carboxy-terminus. Furthermore, it should be noted that a dash at the beginning or end of an amino acid residue sequence indicates a peptide bond to a further sequence of one or more amino-acid residues. The above Table is presented to correlate the three-letter and one-letter notations which may appear alternately herein.

The terms “amino acid modification” or “amino acid substitution” or “substitution,” as used herein, mean an amino acid substitution, insertion, and/or deletion in a polypeptide sequence. An “amino acid substitution” or “substitution” as used herein, means a replacement of an amino acid at a particular position in a parent polypeptide sequence with another amino acid. For example, the substitution L328R refers to a variant polypeptide, in this case a heavy chain constant region variant, in which the leucine at position 328 is replaced with arginine. An “amino acid insertion” or “insertion” as used herein means an addition of an amino acid at a particular position in a parent polypeptide sequence. An “amino acid deletion” or “deletion,” as used herein, means a removal of an amino acid at a particular position in a parent polypeptide sequence.

Amino acid substitutions can be made by mutation (for example mutation of SEQ ID NO:1-65) such that a particular codon in the DNA sequence encoding the polypeptide is changed to a codon which codes for a different amino acid. Such a mutation is generally made by making the fewest nucleotide changes possible. A substitution mutation of this sort can be made to change an amino acid in the resulting protein in a non-conservative manner (i.e., by changing the codon from an amino acid belonging to a grouping of amino acids having a particular size or characteristic to an amino acid belonging to another grouping) or in a conservative manner (i.e., by changing the codon from an amino acid belonging to a grouping of amino acids having a particular size or characteristic to an amino acid belonging to the same grouping). Such a conservative change generally leads to less change in the structure and function of the resulting protein. A non-conservative change is more likely to alter the structure, activity or function of the resulting protein. The embodiments described herein should be considered to include sequences containing conservative changes which do not significantly alter the activity or binding characteristics of the resulting protein.

The following are examples of various groupings of amino acids:

-   -   Amino acids with nonpolar R groups: Alanine, Valine, Leucine,         Isoleucine, Proline, Phenylalanine, Tryptophan, Methionine     -   Amino acids with uncharged polar R groups: Glycine, Serine,         Threonine, Cysteine, Tyrosine, Asparagine, Glutamine     -   Amino acids with charged polar R groups (negatively charged at         Ph 6.0): Aspartic acid, Glutamic acid     -   Basic amino acids (positively charged at pH 6.0): Lysine,         Arginine, Histidine (at pH 6.0)

Another grouping may be those amino acids with phenyl groups: Phenylalanine, Tryptophan, Tyrosine.

Another grouping may be according to molecular weight (i.e., size of R groups) as shown below:

Glycine 75 Alanine 89 Serine 105 Proline 115 Valine 117 Threonine 119 Cysteine 121 Leucine 131 Isoleucine 131 Asparagine 132 Aspartic acid 133 Glutamine 146 Lysine 146 Glutamic acid 147 Methionine 149 Histidine (at pH 6.0) 155 Phenylalanine 165 Arginine 174 Tyrosine 181 Tryptophan 204

The term “antibody” or “antibodies” as used herein includes full length antibodies and antibody fragments, and includes both monoclonal and polyclonal antibodies. An antibody may also include recombinant, genetically engineered or otherwise modified forms of immunoglobulins, such as intrabodies, peptibodies, minibodies, chimeric antibodies, fully human antibodies, humanized antibodies, bispecific antibodies, and antibody fusions or heteroconjugate antibodies (e.g., diabodies, triabodies, and tetrabodies), An “antibody fragment” as used herein includes antibodies that comprise Fc regions, Fc fusions, and the constant region of the heavy chain (CH1-hinge-CH2-CH3), again also including constant heavy region fusions. Specific antibody fragments may include, but are not limited to, (i) the Fab fragment including VL, VH, CL and CH1 domains, (ii) the Fd fragment including of the VH and CH1 domains, (iii) the Fv fragment including of the VL and VH domains of a single antibody; (iv) the dAb fragment (Ward et al. 1989, Nature 341:544-546) which includes of a single variable, (v) isolated CDR regions, (vi) F (ab′) 2 fragments, a bivalent fragment that includes two linked Fab fragments (vii) single chain Fv molecules (scFv), wherein a VH domain and a VL domain are linked by a peptide linker which allows the two domains to associate to form an antigen binding site (Bird et al., 1988; Huston et al., 1988), (viii) bispecific single chain Fv dimers (PCT/US92/09965) and (ix) “diabodies” or “triabodies”, multivalent or multispecific fragments constructed by gene fusion (Tomlinson et. al., 2000, Methods Enzymol. 326:461-479; W094/13804; Holliger et al., 1993, Proc. Natl. Acad. Sci. U.S.A. 90:6444-6448). The antibody fragments may be modified. For example, the molecules may be stabilized by the incorporation of disulphide bridges linking the VH and VL domains (Reiter et al., 1996).

An antibody typically includes a tetrameric structure. Each tetramer is typically composed of two identical pairs of polypeptide chains, each pair having one “light” (typically having a molecular weight of about 25 kDa) and one “heavy” chain (typically having a molecular weight of about 50-70 kDa). Human light chains are classified as kappa and lambda light chains. Heavy chains are classified as mu, delta, gamma, alpha, or epsilon, and define the antibody's isotype as IgM, IgD, IgG, IgA, and IgE, respectively. IgG has several subclasses, including, but not limited to IgG1, IgG2, IgG3, and IgG4. IgM has subclasses, including, but not limited to, IgM1 and IgM2. Thus, “isotype” as used herein is meant any of the subclasses of immunoglobulins defined by the chemical and antigenic characteristics of their constant regions. The known human immunoglobulin isotypes are IgG1, IgG2, IgG3, IgG4, IgA1, IgA2, IgM1, IgM2, IgD, and IgE.

The terms “CDC” or “complement dependent cytotoxicity,” as used herein, mean a reaction wherein one or more complement protein components recognize bound antibody on a target cell and subsequently cause lysis of the target cell.

The “CH2 domain” of a human IgG Fc region (also referred to as “Cy2” domain) usually extends from about amino acid 231 to about amino acid 340. The CH2 domain is unique in that it is not closely paired with another domain. Rather, two N-linked branched carbohydrate chains are interposed between the two CH2 domains of an intact native IgG molecule. It has been speculated that the carbohydrate may provide a substitute for the domain-domain pairing and help stabilize the CH2 domain. Burton, Molec. Immunol. 22:161-206 (1985).

The “CH3 domain” includes the stretch of residues C-terminal to a CH2 domain in an Fc region (i.e. from about amino acid residue 341 to about amino acid residue 447 of an IgG).

The terms “chimeric antibody,” “chimeric antibodies,” “humanized antibody,” and “humanized antibodies” generally refer to antibodies that combine antibody regions (scaffold or framework regions and variable regions) from more than one species. For example, “chimeric antibodies” traditionally comprise variable region(s) from a mouse (or rat, in some cases) and the constant region(s) from a human. “Humanized antibodies” generally refer to non-human antibodies that have had the variable-domain framework regions swapped for sequences found in human antibodies. Generally, in a humanized antibody, the entire antibody, except the CDRs, is encoded by a polynucleotide of human origin or is identical to such an antibody except within its CDRs. The CDRs, some or all of which are encoded by nucleic acids originating in a non-human organism, are grafted into the beta-sheet framework of a human antibody variable region to create an antibody, the specificity of which is determined by the engrafted CDRs. The creation of such antibodies is described in, e.g., WO 92/11018, Jones, 1986, Nature 321:522-525, Verhoeyen et al., 1988, Science 239:15341536, which are hereby incorporated by reference in their entirety, as if fully set forth herein. “Back mutation” of selected acceptor framework residues to the corresponding donor residues is often required to regain affinity that is lost in the initial grafted construct (U.S. Pat. Nos. 5,530,101; 5,585,089; 5,693,761; 5,693,762; 6,180,370; 5,859,205; 5,821,337; 6,054,297; 6,407,213). A humanized antibody may also comprise at least a portion of an immunoglobulin constant region, typically that of a human immunoglobulin, and thus will typically comprise a human Fc region. Humanized antibodies can also be generated using mice with a genetically engineered immune system (Roué et al., 2004). A variety techniques and methods for humanizing and reshaping non-human antibodies are well known in the art (See Tsurushita & Vasquez, 2004, Humanization of Monoclonal Antibodies, Molecular Biology of B Cells, 533-545, Elsevier Science (USA), and references cited therein). Humanization methods include but are not limited to methods described in Jones et al., 1986; Riechmann et al., 1988; Verhoeyen et al., 1988; Queen et al., 1989; He et al., 1998; Carter et al., 1992; Presta et al., 1997; Gorman et al., 1991; and O'Connor et al., 1998; which are hereby incorporated by reference in their entirety, as if fully set forth herein. Humanization or other methods of reducing the immunogenicity of nonhuman antibody variable regions may include resurfacing methods, as described for example in Roguska et al., 1994, Proc. Natl. Acad. Sci. USA 91:969973, which are hereby incorporated by reference in their entirety, as if fully set forth herein. In one embodiment, the parent or variant antibody has been affinity matured, as is known in the art. Structure-based methods may be employed for humanization and affinity maturation, for example as described in U.S. Ser. No. 11/004,590, which is hereby incorporated by reference in its entirety, as if fully set forth herein. Selection based methods may be employed to humanize and/or affinity mature antibody variable regions, including but not limited to methods described in Wu et al., 1999; Baca et al., 1997; Rosok et al., 1996; Rader et al., 1998 and Krauss et al., 2003, which are hereby incorporated by reference in their entirety, as if fully set forth herein. Other humanization methods may involve the grafting of only parts of the CDRs, including but not limited to methods described in U.S. Ser. No. 09/810,502; Tan et al., 2002, J. Immunol, all of which are hereby entirely incorporated by reference. Other humanization methods may involve the grafting of only parts of the CDRs, including but not limited to methods described in U.S. Ser. No. 09/810,502; Tan et al., 2002; De Pascalis et al., 2002, which are hereby incorporated by reference in their entirety, as if fully set forth herein.

The term “constant domain,” as used herein, refers to the portion of an immunoglobulin molecule having a more conserved amino acid sequence relative to other portions of the immunoglobulin, the variable domain, which contains the antigen binding site. The constant domain contains the CH1, CH2 and CH3 domain of the heavy chain and the CL domain of the light chain.

The term “effector function,” as used herein, is a biochemical event that results from the interaction of an antibody Fc region with an Fc receptor or ligand. Effector functions include, but are not limited to, Fcγ R-mediated effector functions such as ADCC and ADCP, and complement-mediated effector functions such as CDC.

The term “effector cell,” as used herein, is a cell of the immune system that expresses one or more Fc receptors and mediates one or more effector functions. Effector cells include but are not limited to monocytes, macrophages, neutrophils, dendritic cells, eosinophils, mast cells, platelets, B cells, large granular lymphocytes, Langerhans' cells, natural killer (NK) cells, and T cells, and may be from any organism including but not limited to humans, mice, rats, rabbits, and monkeys.

The terms “Fab” or “Fab region,” as used herein, mean one or more polypeptides that comprise the VH, CH1, VL, and CL immunoglobulin domains. Because VL includes the JL region and VH includes the JH region, JL and JH also compose the Fab region. It is generally viewed in the art that the Fab region is demarcated N-terminally by the N-terminus and C-terminally by the disulfide bond that covalently links the heavy and light chains. Accordingly, for the purposes of the embodiments described herein, “Fab region” as used herein includes amino acids positions from the N-terminus to position 214 of the light chain and from the N-terminus to position 220 of the heavy chain, wherein the numbering of the C-terminal residues is according to the EU numbering scheme. Fab may refer to this region in isolation, or this region in the context of a full-length antibody or antibody fragment. Positional definitions of the regions within the Fab, including the VL, VH, JL, JH, CL, and CH1 regions, are illustrated in FIG. 1). The VL kappa and VH regions are well defined genetically and in the art, and accordingly “VL region” as used herein includes residues 1-107, and “VH region” as used herein includes residues 1-113, wherein numbering is according to the Kabat numbering scheme. The JL kappa region is made up of 5 germ line sequences of equal length, and accordingly, “JL region,” as used herein, includes positions 96-107, wherein numbering is according to Kabat. There are 6 JH germ line sequences of differing length, and the exact Kabat position at which this segment combines with the VH germ line varies. For the purposes of the embodiments described herein, the JH region may comprise the residues of these sequences that are clearly defined in a Kabat sequence alignment. Based on this definition, “JH region” as used herein includes residues 100-113, wherein numbering is according to the Kabat numbering scheme. The remaining C-terminal light and heavy chain sequences of the Fab are made up of the CL and CH1 regions respectively. Thus, “CL region” as used herein includes positions 108-214, and “CH1 region” as used herein includes positions 118-220, wherein numbering is according to the EU numbering scheme. Fab may refer to this region in isolation, or this region in the context of a full-length antibody or antibody fragment.

The terms “Fc Binding protein” or “FcBP,” as used herein, mean a microbial product that can bind to an immunoglobulin through interaction with the Fc region of the immunoglobulin. Examples of such proteins include SpA and Protein G which interact with the CH2-CH3 interface of the immunoglobulin Fc region, or SSL10 which interacts with IgG1 at site which is distinct from the SpA binding site.

The term “Fc fusion,” as used herein, is a protein wherein one or more polypeptides are operably linked to Fc. Fc fusion is herein meant to be synonymous with the terms “immunoadhesin”, “Ig fusion”, “Ig chimera”, and “receptor globulin” (sometimes with dashes) (Chamow et al., 1996, Trends Biotechnol 14:52-60; Ashkenazi et al., 1997, Curr Opin Immunol 9:195-200, both hereby entirely incorporated by reference). An Fc fusion combines the Fc region of an immunoglobulin with a fusion partner, which in general may be any protein, polypeptide or small molecule. The role of the non-Fc part of an Fc fusion, i.e., the fusion partner, is to mediate target binding, and thus it is functionally analogous to the variable regions of an antibody. In addition to Fc fusions, “antibody fusions” include the fusion of the constant region of the heavy chain with one or more fusion partners or conjugate partners (again including the variable region of any antibody), while other antibody fusions are substantially or completely full length antibodies with fusion partners or conjugate partners. In one embodiment, a role of the fusion or conjugate partner is to mediate target binding, and thus it is functionally analogous to the variable regions of an antibody (and in fact can be). Virtually any protein or small molecule may be linked to Fc to generate an Fc fusion or antibody fusion. Protein fusion or conjugate partners may include, but are not limited to, the target binding region of a receptor, an adhesion molecule, a ligand, an enzyme, a cytokine, a chemokine, or some other protein or protein domain. Small molecule fusion partners may include any therapeutic agent that directs the Fc fusion to a therapeutic target. Such targets may be any molecule, such as an extracellular receptor that is implicated in disease. The fusion or conjugate partner can be proteinaceous or non-proteinaceous; the latter generally being generated using functional groups on the antibody and on the conjugate partner. For example, linkers are known in the art; for example, homo- or hetero-bifunctional linkers as are well known (see, 1994 Pierce Chemical Company catalog, technical section on cross-linkers, pages 155-200, incorporated herein by reference).

The term “Fc gamma receptor” or “Fcγ R,” as used herein, is any member of the family of proteins that bind the IgG antibody Fc region and are substantially encoded by the Fcγ R genes. In humans, this family includes, but is not limited to, Fcγ RI (CD64), including isoforms FcγRIa, FcγRIb, and FcγRIc; Fcγ RII (CD32), including isoforms FcγRIIa (including allotypes H131 and R13I), FcγRIIb (including FcγRIIb-1 and FcγRIIb-2), and FcγRIIc; and FcγRIII (CDI6), including isoforms FcγRIIIa (including allotypes VI58 and F158) and FcγRIIIb (including allotypes FcγRIIIb-NAI and Fcγ RIIIb-NA2) (Jefferis et al., 2002, Immunol Lett 82:57-65, which is hereby entirely incorporated by reference), as well as any undiscovered human Fcγ Rs or Fcγ R isoforms or allotypes. An Fcγ R may be from any organism, including but not limited to humans, mice, rats, rabbits, and monkeys. Mouse Fcγ Rs include but are not limited to Fcγ RI (CD64), Fcγ RII (CD32), Fcγ RIII (CDI6), and Fcγ RIII-2 (CDI6-2), as well as any undiscovered mouse Fcγ Rs or Fcγ R isoforms or allotypes.

The term “Fc ligand,” as used herein, is a molecule, such as a polypeptide, from any organism that binds to the Fc region of an antibody to form an Fc/Fc ligand complex. Fc ligands include, but are not limited to, Fcγ Rs, Fcγ Rs, Fcγ Rs, FcRn, Clq, C3, mannan binding lectin, mannose receptor, staphylococcal SpA, streptococcal protein G, and viral Fcγ R. Fc ligands also include Fc receptor homologs (FcRH), which are a family of Fc receptors that are homologous to the Fcγ Rs (Davis et al., 2002, Immunological Reviews 190:123-136, which is hereby entirely incorporated by reference). Fc ligands may include undiscovered molecules that bind Fc.

The terms “Fc” or “Fc region,” as used herein, mean a polypeptide that includes the heavy chain constant region of an antibody excluding the first heavy chain constant region immunoglobulin domain. Thus Fc refers to the last two heavy chain constant region immunoglobulin domains of IgA, IgD, and IgG, and the last three constant region immunoglobulin domains of IgE and IgM, and the flexible hinge N-terminal to these domains. For IgA and IgM, an Fc may include the J chain. For IgG, as illustrated in FIG. 1, Fc includes immunoglobulin domains Cgamma2 and Cgamma3 (Cγ2 and Cγ3) and the hinge between C gamma 1 (Cγ1) and Cgamma2 (Cγ2). Cγ1, Cγ2 and Cγ3 are also commonly referred to as CH1, CH2 and CH3. Although the boundaries of the Fc region may vary, the human IgG heavy chain Fc region is usually defined to comprise residues C226 or P230 to its carboxyl-terminus, wherein the numbering is according to the EU index as in Kabat. Fc may refer to this region in isolation, or this region in the context of an Fc polypeptide, as described below. The term “Fc polypeptide,” as used herein, is a polypeptide that includes all or part of an Fc region. Fc polypeptides include, but are not limited to, antibodies, Fc fusions, isolated Fcs, and Fc fragments. Therefore, “outside the Fc region” as used herein means the region of an antibody that does not comprise the Fc region of the antibody. In accordance with the aforementioned definition of Fc region, “outside the Fc region” for an IgG1 antibody is herein defined to be from the N-terminus up to and including residue T225 or C229, wherein the numbering is according to the EU numbering scheme. Thus, the Fab region and part of the hinge region of an antibody are outside the Fc region.

The term “full length antibody,” as used herein, is a structure that is or includes the natural biological form of an antibody, including variable and constant regions. For example, in most mammals, including humans and mice, the full length antibody of the IgG isotype is a tetramer and includes two identical pairs of two immunoglobulin chains, each pair having one light and one heavy chain, each light chain that includes immunoglobulin domains VL and CL; and each heavy chain that includes immunoglobulin domains VH, CH1, CH2, and CH3. In some mammals, for example in camels and llamas, IgG antibodies may include only two heavy chains, each heavy chain including a variable domain attached to the Fc region.

A “fully human antibody” or “complete human antibody” refers to a human antibody having the gene sequence of an antibody derived from a human chromosome with the modifications outlined herein.

The term “germline,” as used herein, is the set of sequences that compose the natural genetic repertoire of a protein, and its associated alleles.

The terms “hinge” or “hinge region,” as used herein, mean the flexible polypeptide that includes the amino acids between the first and second constant domains of an antibody. Structurally, the IgG CH1 domain ends at EU position 220, and the IgG CH2 domain begins at residue EU position 237. Thus for IgG the antibody hinge is herein defined to include positions 221 (D221 in IgG1) to 236 (G236 in IgG1), wherein the numbering is according to the EU index as in Kabat. In some embodiments, for example in the context of an Fc region, the lower hinge is included, with the “lower hinge” generally referring to positions 226 or 230.

An immunoglobulin Fc variant or heavy chain constant region variant includes one or more amino acid modifications relative to a parent immunoglobulin Fc polypeptide or heavy chain constant region polypeptide, wherein said amino acid modification(s) provide one or more altered properties. An Fc or heavy chain constant region variant of the embodiments described herein differ in amino acid sequence from its parent IgG by virtue of at least one amino acid modification. Thus, variants described herein have at least one amino acid modification compared to the parent. Alternatively, the variants described herein may have more than one amino acid modification as compared to the parent, for example from about one to fifty amino acid modifications, preferably from about one to ten amino acid modifications, and preferably from about one to about five amino acid modifications compared to the parent. Thus the sequences of the Fc variants or Ig heavy chain constant region variant and those of the parent Fc polypeptide are substantially homologous. For example, the variant heavy chain constant region variant sequences herein will possess about 80% homology with the parent heavy chain constant region variant sequence, preferably at least about 90% homology, and preferably at least about 95% homology. Modifications may be made genetically using molecular biology methods known in the art.

The terms “immunoglobulin BP,” “IgBP” or “microbial immunoglobulin binding protein,” as used herein, mean a microbial product that can bind to immunologic either through interaction with the Fc region of the immunoglobulin (e.g. SpA or Protein G), or though non-immune interaction with the Fab region (e.g. SpA-Fab binding domain), or through interaction with heavy or light chain constant regions outside the Fc region (e.g. L protein of Peptostreptococcus magnus).

The term “immunoglobulin (Ig),” as used herein is a protein including one or more polypeptides substantially encoded by immunoglobulin genes.

Immunoglobulins include but are not limited to antibodies. Immunoglobulins may have a number of structural forms, including but not limited to full-length antibodies, antibody fragments, and individual immunoglobulin domains.

The term “IgG,” as used herein, is a polypeptide belonging to the class of antibodies that are substantially encoded by a recognized immunoglobulin gamma gene. In humans, this IgG includes the subclasses or isotypes IgG1, IgG2, IgG3, and IgG4. In mice, IgG includes IgG1, IgG2a, IgG2b, IgG3.

The term “isotype,” as used herein, is any of the subclasses of immunoglobulins defined by the chemical and antigenic characteristics of their constant regions. The known human immunoglobulin isotypes are IgG1, IgG2, IgG3, IgG4, IgA1, IgA2, IgM, IgD, and IgE.

The term “isotypic modification,” as used herein, is an amino acid modification that converts one amino acid of one isotype to the corresponding amino acid in a different, aligned isotype. For example, because IgG1 has a tyrosine and IgG2 a phenylalanine at EU position 296, a F296Y substitution in IgG2 is considered an isotypic modification.

The term “non-immune binding,” as used herein, refers to binding of an antibody to an IgBP virulence factor that does not involve antigen-dependent binding by the variable region of the antibody. In contrast, the term “immune binding,” as used herein, refers to specific binding of an antigen by an antibody that involves antigen-dependent binding by the variable region of the antibody.

The term “novel modification,” as used herein, is an amino acid modification that is not isotypic. For example, because none of the IgGs have a glutamic acid at position 332, the substitution 1332E in IgG1, IgG2, IgG3, or IgG4 is considered a novel modification.

The terms “parent polypeptide”, “parent protein”, “precursor polypeptide”, or “precursor protein,” as used herein, mean an unmodified polypeptide that is subsequently modified to generate a variant. Said parent polypeptide may be a naturally occurring polypeptide, or a variant or engineered version of a naturally occurring polypeptide. Parent polypeptide may refer to the polypeptide itself, compositions that comprise the parent polypeptide, or the amino acid sequence that encodes it. Accordingly, by “parent Fc polypeptide” as used herein is meant an Fc polypeptide that is modified to generate a variant, and by “parent antibody” as used herein is meant an antibody that is modified to generate a variant antibody.

The terms “parental immunoglobulin,” “parental antibody,” or “parent antibody” as used herein, mean an unmodified immunoglobulin polypeptide that is subsequently modified to generate a variant. Said parent immunoglobulin polypeptide may be a naturally occurring polypeptide, or a variant or engineered version of a naturally occurring polypeptide. Parental immunoglobulin or antibody may refer to the polypeptide itself, compositions that comprise the parental polypeptide, or the amino acid sequence that encodes it.

The term “position” or “amino acid position,” as used herein, is a location in the sequence of a protein or an antibody. Positions may be numbered sequentially, or according to established format. Several formats are known in the art including, but not limited to, EU, Kabat, Chotia, IMGT, AHo, and Abhinandan. One skilled in the art would understand the corresponding “EU position,” “Kabat position,” “Chotia position,” IMGT position,” or “AHo position.” Therefore, any amino acid positions described herein are for identification purposes only, and are not meant to be limited to a particular numbering format.

The term “EU position” or “EU numbering” as used herein, is a location in the sequence of a protein. Positions may be numbered sequentially, or according to an established format, for example the EU position (Edelman, G. M. et al., Proc. Natl. Acad. USA, 63, 78-85 (1969), http://www.imgt.org/IMGTScientificChart/Numbering/IMGTIGVCsuperfamily.html). For example, position 297 is a position in the human antibody IgG1.

The term “Kabat position,” or “Kabat numbering” as used herein, is a location in the sequence of a protein. Positions may be numbered sequentially, or according to an established format, for example the index as in Kabat (Kabat et al., “Sequences of Proteins of Immunological Interest”, NIH Publication, 91-3242 (1991), http://www.imgt.org/IMGTScientificChart/Numbering/IMGTIGVCsuperfamily.html).

A “polypeptide” or “protein,” as used herein, is at least two covalently attached amino acids, which includes proteins, polypeptides, oligopeptides and peptides.

The term “residue,” as used herein, is an amino acid, or a position in a protein and its associated amino acid identity. For example, Asparagine 297 (also referred to as Asn297, Asn 297, N297 or 297N) is a residue in the human antibody IgG1.

A “replicon” is any genetic element (e.g., plasmid, chromosome, virus) that functions as an autonomous unit of DNA replication in vivo; i.e., capable of replication under its own control.

Two DNA sequences are “substantially homologous” when at least about 75% (preferably at least about 80%, and preferably at least about 90 or 95%) of the nucleotides match over the defined length of the DNA sequences. Sequences that are substantially homologous can be identified by comparing the sequences using standard software available in sequence data banks, or in a Southern hybridization experiment under, for example, stringent conditions as defined for that particular system. Defining appropriate hybridization conditions is within the skill of the art. See, e.g., Maniatis et al., supra; DNA Cloning, Vols. I & II, supra; Nucleic Acid Hybridization, supra, which are hereby incorporated in their entirety as if fully set forth herein.

The term “target cell,” as used herein, is a cell that expresses a target antigen.

The term “variable region” or “variable domain” as used herein, is the region of an immunoglobulin that includes one or more Ig domains substantially encoded by any of the VK′ VL and/or VH genes that make up the kappa, lambda, and heavy chain immunoglobulin genetic loci respectively.

The terms “variant polypeptide”, “polypeptide variant”, “variant immunoglobulin”, “variant antibody” or “variant,” as used herein, refer to a polypeptide sequence that differs from that of a parental polypeptide sequence by virtue of at least one amino acid modification. The parent polypeptide may be a naturally occurring or wild-type (WT) polypeptide, or may be a modified version of a WT polypeptide. Variant polypeptide may refer to the polypeptide itself, a composition that includes the polypeptide, or the amino sequence that encodes it. The variant polypeptide may have at least one amino acid modification compared to the parent polypeptide, e.g. from about one to about ten amino acid modifications, or from about one to about five amino acid modifications compared to the parent. The variant polypeptide sequence hereinmay possess at least about 80% homology with a parent polypeptide sequence, at least about 90% homology, or at least about 95% homology.

Accordingly, the terms “Fc variant”, “variant Fc” or “variant immunoglobulin” or “variant antibody,” as used herein, mean an antibody sequence that differs from that of a parent sequence by virtue of at least one amino acid modification. An Fc variant may only encompass an Fc region, or may exist in the context of an antibody, Fc fusion, isolated Fc, Fc fragment, or other polypeptide that is substantially encoded by Fc. Fc variant may refer to the Fc polypeptide itself, compositions including the Fc variant polypeptide, or the amino acid sequence that encodes it. The terms “Fc polypeptide variant” or “variant Fc polypeptide,” as used herein, refer to an Fc polypeptide that differs from a parent Fc polypeptide by virtue of at least one amino acid modification. The terms “protein variant” or “variant protein,” as used herein, mean a protein that differs from a parent protein by virtue of at least one amino acid modification. The terms “antibody variant” or “variant antibody,” as used herein, mean an antibody that differs from a parent antibody by virtue of at least one amino acid modification. The terms “IgG variant” or “variant IgG,” as used herein, mean an antibody that differs from a parent IgG by virtue of at least one amino acid modification. The terms “immunoglobulin variant” or “variant immunoglobulin,” as used herein, mean an immunoglobulin sequence that differs from that of a parent immunoglobulin sequence by virtue of at least one amino acid modification.

Accordingly, the terms “heavy chain constant region variant”, “variant heavy chain constant region,” “heavy chain constant region variant,” “variant heavy chain constant region,” “variant immunoglobulin,” or “variant antibody,” as used herein, mean a heavy chain constant region antibody sequence that differs from that of a parent sequence by virtue of at least one amino acid modification. A heavy chain constant region variant may include an heavy chain constant region alone, or may exist in the context of an antibody, a heavy chain constant region fusion, isolated heavy chain constant region, heavy chain constant region fragment, or other polypeptide that is substantially encoded by heavy chain constant region. Heavy chain constant region variant may refer to the heavy chain constant region polypeptide itself, compositions that include the heavy chain constant region variant polypeptide, or the amino acid sequence that encodes it. The terms “heavy chain constant region polypeptide variant” or “variant heavy chain constant region polypeptide,” as used herein, refer to a heavy chain constant region polypeptide that differs from a parent heavy chain constant region polypeptide by virtue of at least one amino acid modification.

The terms “protein variant” or “variant protein,” as used herein, mean a protein that differs from a parent protein by virtue of at least one amino acid modification. The terms “antibody variant” or “variant antibody,” as used herein, mean an antibody that differs from a parent antibody by virtue of at least one amino acid modification. The terms “IgG variant” or “variant IgG,” as used herein, mean an antibody that differs from a parent IgG by virtue of at least one amino acid modification. The terms “immunoglobulin variant” or “variant immunoglobulin,” as used herein, mean an immunoglobulin sequence that differs from that of a parent immunoglobulin sequence by virtue of at least one amino acid modification.

The term “wild type or WT,” as used herein, is an amino acid sequence or a nucleotide sequence that is found in nature, including allelic variations. A WT protein, polypeptide, antibody, immunoglobulin, IgG, etc. has an amino acid sequence or a nucleotide sequence that has not been intentionally modified antibodies. Accordingly, the present disclosure provides variant antibodies.

The following examples are intended to illustrate various embodiments of the invention. As such, the specific embodiments discussed are not to be construed as limitations on the scope of the invention. It will be apparent to one skilled in the art that various equivalents, changes, and modifications may be made without departing from the scope of invention, and it is understood that such equivalent embodiments are to be included herein. Further, all references cited in the disclosure are hereby incorporated by reference in their entirety, as if fully set forth herein.

EXAMPLES

The embodiments described herein is more fully understood by reference to the following examples. They should not however be construed as limiting the scope of the invention. All literature and patent citations mentioned herein are expressly incorporated by reference herein as if fully set forth herein.

The disclosure involves both the generation of anti-microbial variable domain polypeptides, which constitute the antigen-binding site of the antibody, and their combination with immunoglobulin light and heavy chain constant region sequences and their variants. The resulting variant antibodies have antimicrobial activity. The first section of the examples covers the generation of variable domain anti-microbial antibodies. In the examples profiles the anti-microbial antibodies are directed against S. aureus antigens SpA and ClfA. The second section covers the generation of heavy chain constant regions and their variants. The third section covers the construction, expression and purification of antibodies and their variants and the final section covers biological testing of example anti-microbial immunoglobulins and their heavy chain constant region variants.

Examples are provided that demonstrate the enhanced anti-microbial activity of Fc variant anti-Microbial antibodies.

Anti-Microbial Antibody Generation

Anti-S. aureus Antibodies

In some embodiments where the target microbe is S. aureus, heavy chain constant region variant IgG polypeptide sequences are combined with immunoglobulin heavy chain variable polypeptide sequences and light chains polypeptide sequences, which bind one or more cell surface or secreted S. aureus antigen. Examples of S. aureus antigen recognized by the variable domain of heavy chain constant region variant IgG antibodies are cell surface or secreted antigens selected from the list which includes but is not limited to: ClfA, ClfB, Cna, Eap, Ebh, EbpS, FnBPA, FnBPB, IsaA, IsaB, IsdA, IsdB, IsdH, SasB, SasC, SasD, SasF, SasG, SasH, SasK, SdrC, SdrD, SdrE, Spa, SraP, Coa, Ecb, Efb, Emp, EsaC, EsxA, EssC, FLIPr, FLIPr like, Sbi, SCIN-B, SCIN-C, VWbp, SpA, LTA, CP5, CP8, PNAG, dPNAG, alpha toxin, CHIPS, PVL leukocidin, α, β and γ-hemolysins, SAK, Sea, Sep, Seb, Epa, Efb, SCIN, Exfoliatins ETB and ETA, Staphylococcal Enterotoxins SEA, SEB, SECn, SED, SEG, SHE, and SEI, Toxic-shock syndrome toxin TSST-1, Alpha Toxin, Beta toxin, Delta toxin.

As examples of the utility, anti-SpA and anti-ClfA parental and heavy chain constant region variant IgG1 antibodies have been generated. Additionally, control heavy chain constant region variant IgG1 antibodies which target an unrelated viral antigen (anti-RSV variable domain) have been produced to enable characterization of microbial IgBP binding to the heavy chain constant region variants in the absence of microbial binding by the variable domain of the antibody. The following examples illustrate the generation of anti-S. aureus antibodies (including humanization of exemplar murine antibodies) and their combination with example variant heavy chain constant regions described herein.

Example 1: Epitope Discovery and Generation of Anti-SpA Monoclonal Antibodies (by In Vivo Immunization and Humanization)

In Silico Discovery of Anti-SpA Antigens and Epitopes.

The SpA amino acid sequence from 2 strains of S. aureus (Newman and USA 300) was initially examined (FIG. 2). Regions of high inter IgBP domain (SpA domains E, D, A, B and C) sequence homology were found which primarily mapped to region of Helices I, II and III. Models of the binding interfaces of domain B (only Helix I and II are shown for clarity) of SpA with an IgG Fc fragment (FIG. 8, derived from PDB ID: 1FC2) and the SpA domain D with a IgM VH3 Fab fragment (FIG. 9, derived from PDB ID 1DEE) were constructed from X-ray structures available within the PDB database.

The individual SpA IgBP domains (domains E, D, A, B and C) each adopt three-helix bundles (FIG. 9 represents the SpA D domain). One face, includes residues from helices I and II binds, IgG Fc (FIG. 8). Residues from helices II and III on the other face bind VH3 Ig (FIG. 9) (Deisenhofer, 1981; Graille et al., 2000).

The amino residues that vary between individual IgBP domains of SpA, referred to as inter-domain variable residues were mapped onto the model and analyzed (e.g., residues indicated by arrows in FIG. 8 and FIG. 9).

With respect to Fc binding, it was found that inter-domain variable residues mapped to the face of helix I and II that are not involved directly in interactions with the IgG Fc region. Most inter-domain variable residues are located on the non Fc interacting face of Helix I and II, the N terminus of Helix I, and the amino acid chain the connects Helix I and II (FIG. 8).

A similar strategy was taken to analyze residues that are involved in interaction between SpA IgBP domains and VH3 derived Fab sequences (FIG. 3). As shown in FIG. 9, residues involved in the interaction between SpA IgBP Helix II and III of domain D are highly conserved in Domains E, A, B and C. Inter-domain variable residues have been mapped onto the model shown in FIG. 9 (monomer of SpA domain D and a VH3 Fab fragment). Most inter-domain variable residues are located on the non-Fab interacting face of Helix II and III.

The amino acid sequence of the individual SpA IgBP domains from sequenced stains of S. aureus were obtained from public sequence data bases and analyzed for intra-domain strain sequence variability. The aligned sequences are shown in FIGS. 11A-E. The amino acid residues involved with binding to IgFc (FIGS. 8A-B) and VH3 Fab residues (FIGS. 9A, B, C) are highly conserved in all sequenced stains (FIGS. 11A-E). This finding demonstrates a high degree of functional (Fc and VH3 Fab binding residues) conservation of amino acid residues within SpA IgBP domains of sequenced stains.

In the stains analyzed, no substitutions were found in SpA domain C (FIG. 11C).

Within SpA domains E, D, A and B, inter-strain sequence changes within individual SpA domains were highly conservative with respect to function. In almost all cases, if a substitution occurred, it is changed to an amino acid that is found in one of the other SpA domains, and the position is not important for the interacting with either Fc or VH3 Fab (FIGS. 11A-E).

For example a number of stains have a Q to K substitution within Helix III of SpA domain E (FIGS. 11-E). K is found at the same position in all sequenced stains of S. aureus domains D, A, B and C that were analyzed (FIGS. 11A-D). The position of the Q to K substitution in domain E is located on the face of Helix III that does not interact with the VH3 Fab (FIG. 10).

Based on the analysis of sequence, a number of different SpA epitopes were identified that would be highly conserved in SpA domains within a S. aureus strain, and which are also highly conserved between S. aureus stains. These epitopes cover the functionally concerned Fc and Fab binding faces of SpA domains. Such epitopes, which involve SpA binding interfaces required for virulence functions, would be used when targeting anti-microbial antibodies to S. aureus, as they would be less prone to the selection of resistance since a) the epitopes are present in multiple SpA domains, b) mutations within such epitopes are likely to abrogate the virulence function of the SpA domain in which they occur.

Additionally, the repeat nature of the epitope in multiple SpA domains will enhance antibody avidity. Such antibodies will neutralize one or more IgBP virulence functions of SpA and target opsono-phagocytosis to SpA coated target microbes.

A number of antibody binding regions of SpA were identified. These regions are involved in functional interactions between SpA and Fc and/or Fab. Directing antibody binding to epitopes, which involve these functional binding interfaces, or selecting antibodies with such properties, is an important aspect of the embodiments described herein.

One SpA binding region that was identified is the binding interface of Helix I and II that interacts with IgFc. Epitopes, which involve this interface, will be highly conserved between SpA domains and strains. Additionally, monoclonal antibodies recognizing such epitopes will block Fc binding and may also block vWF and TNFR1 binding to SpA domains to which they bind. In the case in which the epitope to which the antibody binds involves Helix II, VH3 Fab binding to SpA is also likely to be blocked.

Another SpA binding region that was identified covers Helix II, which is involved in interacts with both IgFc and VH3 Fab. Binding of monoclonal antibodies to SpA epitopes within this highly conserved Helix, which can block both Fc and Fab binding to SpA. As Helix II is virtually invariant between SpA domains and between S. aureus stains, this region of SpA is a target of antibodies described herein.

One SpA binding region that was identified is the binding interface of Helix II and III that interacts with Ig VH3 Fab. Binding of monoclonal antibodies to SpA epitopes within this region are highly conserved between SpA domains and strains. Additionally, monoclonal antibodies recognizing such epitopes will block VH3 Fab binding and may also block Fc binding to SpA.

Immunization or selection methods for the selection of antibodies that recognize conserved SpA epitopes are provided.

The IgFc binding domains of Sbi (I and II) were also analyzed (FIGS. 12, 13 and 14). Amino acids within the predicted Helix I region are highly conserved between Sbi domains I and II (FIG. 12B) and also between Sbi domains and Spa Fc binding helix I and a number of amino acids in Helix II (FIG. 12B). Invariant residues were mapped onto the model of Spa domain D (Helix I and II) binding to the Fc region of an IgG (FIG. 13). As can be seen, residues that interact with IgFc are conserved between Spa domains and Sbi domains. In addition to these invariant residues, a number of highly conservative residues are found in Sbi that are present in some SpA domains (FIG. 12).

The amino acid sequence of the individual Sbi IgBP domains from sequenced stains of S. aureus were obtained from public sequence databases and analyzed for intra-domain strain sequence variability (FIG. 14). The aligned sequences are shown in FIG. 14 (panel A (Sbi domain I) and panel B (Sbi domain II)). In the stains analyzed, no substitutions were found in Sbi domain I (FIG. 14A). Only a single inter-strain change was found in domain II (FIG. 14B) located within Helix 1 (N to S substitution in strain CC239_JKD6009). This position is not conserved between domains I and II, and also differs between SpA domains E and the residue found in domains D, A, B and C. Mapping of the location of this residue onto the SpA model shows that this residue is not directly involved in interaction with the IgG Fc binding interface (FIG. 15).

Thus, the Fc binding interface of Sbi and SpA are conserved within and between S. aureus strains. The conserved Fc binding interfaces of Sbi and SpA domains are attractive targets for raising monoclonal antibodies. Such antibodies will neutralize one or more virulence functions of the SpA or Sbi domain to which they bind. Additionally, such antibodies will have anti S. aureus activity.

Example 2: Murine, Human or Humanized Antibodies Generation

Immunization or selection methods for the selection of cross-reactive antibodies (i.e. antibodies that recognize multiple SpA IgBP domains and/or Sbi domains) are provided.

In the case where antibodies are derived from wild type mice, such as female Swiss Webster Mice, the murine monoclonal antibodies selected may be humanized by CDR grafting using methods known in the art (Almagro and Fransson (2008)).

In an alternative method, human antibodies can be obtained directly using transgenic mice methods such as VelocImmune®. VelocImmune® is a mouse with a genetically humanized immune system, which can be used to greatly increase the speed and efficiency of in-vivo generation of fully-human therapeutic antibodies (Lonberg N (2005)).

In yet an alternative method, antibody domain fragments can be selected using Display technologies such as phage, yeast and ribosome display using methods known in the art. Following reformatting, such antibodies can be affinity matured, if required, to high affinity by methods known in the art (Hoogenboom H R (2005)).

Alternatively, human antibody variable domains can be selected from mammalian display libraries using methods known in the art. Such antibodies can be affinity matured to high affinity by methods known in the art (Bowers et al., 2011).

An alternative antibody discovery method exploits high-throughput DNA sequencing to analyze the VL and VH gene repertoires derived from the mRNA transcripts of fully differentiated mature B cells or antibody-secreting Bone Marrow Plasma Cells from SpA immunized mice as described by Reddy (Reddy et al, 2010). After a bioinformatics analysis, abundant VL and VH gene sequences are identified within the repertoire of each immunized mouse. VL and VH genes are then paired according to their relative frequencies within the repertoire. Antibody VH and VL genes are synthesized by oligonucleotide and PCR assembly. Recombinant antibodies can be expressed in bacterial and mammalian systems as single-chain variable fragments (scFv), or full-length chimeric variant IgG1 antibodies respectively. Antibodies of interest can then be humanized and affinity matured using methods know to those practicing the art (CDR grafting followed by affinity maturation).

In an alternative method, human antibodies can be isolated from patients or volunteers following recovery from a microbial infection or immunization with a vaccine against the target microbe (Wrammert et al., 2008)

Example 3: In Vivo Immunization and Selection of Anti-SpA and Anti-Sbi Antibodies

Immunization Protocol: Mice may be used in this procedure. The SpA antigen used as an antigen for immunization can be obtained from a number of commercial sources or by standard molecular biology methods known in the art. Alternatively, recombinant SpA (e.g. Thermo Fisher Scientific cat #21184) or individual Ig binding domains or combinations of SpA domains (selected from the list: SpA domain A, B, C, D or E), can be produced using standard recombinant technology. Immunization of wild type or transgenic animals (Lonberg N (2005), Almagro and Fransson (2008)) are effective method for generating antibodies to many antigens.

For antibody screening following immunization, subjects can be bled two weeks after each immunization booster and non-pooled samples can be checked for anti-SpA antibodies according to the protocol described below. Due to the interaction of murine and human isotypes with SpA via the Fc domain, murine IgG1 or human IgG3 are often used for screening to avoid interference from non-immune IgBP binding to the SpA antigen.

The ELISA format that can be used to screen for antibodies is as follows: In one example ELISA plates (e.g. Nunc MaxiSorp 96 well plates) are coated with goat anti murine IgG1 antibody and then blocked using the manufacturers recommended method. Following washing, dilutions of murine serum samples are added to wells and incubated. Following washing of the plates to remove unbound materials, peroxidase conjugated antigen, such as SpA or Sbi, is added to plates. In the case of anti-SpA murine antibodies, Mild Elution Buffer pH 6.0 (Thermo Scientific cat #21033) is used for plate washing. At this pH, binding of SpA to murine IgG1 via the Fc domain of the antibody minimal. Following washing at pH 6.0 with Mild Elution Buffer pH 6.0 (Thermo Scientific cat #21033) to remove unbound conjugate, anti-SpA murine IgG1 is detected using standard Peroxidase reagents and the absorbency signal is read.

Alternatively, engineered SpA antigens can be used which contains point mutations (Kim et al., 2010, 2102) which abolishes Fc binding to domains A, B, C, D and E of SpA (SpA KK containing the following substitutions in each SpA domain: Q9K and Q10K or SpA KKAA containing the following substitutions in each SpA domain: Q9K, Q10K, D36A and D37A (Kim et al., 2010)). To determine SpA specific serum IgG, affinity purified SpA KK or SpA KKAA can be used to coat ELISA plates (NUNC Maxisorp) at 1 μg·ml-1 in 0.1 M carbonate buffer (pH 9.5 at 4° C.) overnight. The following day, plates are blocked and incubated with dilutions of hyperimmune sera and developed using OptEIA reagent (BD Biosciences).

Fusion Protocol.

The mouse selected for fusion is boosted with the same dose of antigen used in previous immunizations. The booster regime may be administered over the four-day period prior to splenectomy and cell fusion. Alternatively, the animal can be boosted with recombinant protein consisting of individual IgBP SpA domains from the same of a different S. aureus strain, or combinations of domains selected from the list: SpA domain A, B, C, D or E.

In another strategy designed to identify antibodies that cross-react with multiple SpA domains, the primary immunization uses one isolated SpA domain, and the booster includes a different domain or domains than used for the primary immunization. The booster regime may be administered over the four-day period prior to splenectomy and cell fusion.

In another strategy designed to identify antibodies that cross react with SpA and Sbi, the booster can be recombinant IgBP Sbi domain I, II or I and II. Such a strategy is designed to select for antibodies that recognize a conserved interaction interface between both SpA and Sbi and Fcγ.

In yet another immunization strategy, Domain I and II of Sbi can be used for the primary immunization, and SpA, or its individual Ig binding domains selected from the list domain A, B, C, D or E, can be used as a booster. Such a strategy will select for antibodies that cross reacting with epitopes that are found on the FcBP domains of Sbi domain I or II and one or more Spa domains selected from the list: domain A,B,C,D and E. Such a strategy is designed to select for antibodies that recognize a conserved interaction interface between both SpA and Sbi and Fcγ.

On the day of fusion the selected mouse is sacrificed and the spleen is removed aseptically. The spleen may be minced using forceps and strained through a sieve. The cells may be washed twice using IMDM medium (Iscove's Modified DMEM with L-glutamine and 25 mM HEPES, Cellgro catalog number 10-016-CM; Mediatech, Inc., Herndon, Va.) and counted using a hemocytometer. The mouse myeloma cell line should be removed from static log-phase culture. The cell are washed with IMDM twice and counted using a hemocytometer.

Myeloma and spleen cells should then be mixed in a 1:5 ratio and centrifuged. The supernatant is discarded. The cell pellet is then gently resuspended by tapping the bottom of the tube. One milliliter of a 50% solution of PEG (MW 1500) is added (drop by drop) over a period of 30 seconds. The pellet is mixed gently for 30 seconds using a pipette. The resulting cell suspension is allowed to stand undisturbed for another 30 seconds. One milliliter (mL) of IMDM is then added over a period of one minute, followed by the drop wise addition of two mL of IMDM over a period of two minutes. Another five mL of IMDM is added immediately the two-minute period. The resulting cell suspension may be left undisturbed for 5 minutes.

The cell suspension may be centrifuged at room temperature for 10 minutes at 1200 rpm. The pellet is then resuspended in HAT medium (IMDM containing 10% FBS, 2 mM L-glutamine, 0.6% 2-mercaptoethanol (0.04% solution), hypoxanthine, aminopterin, thymidine, and 10% Origen growth factor). The cells are resuspended to 1×10⁶ cells per milliliter. Cell suspensions are plated into 96-well plates. Two hundred microliters (or approximately 2×10⁵ cells) are added to each well. The 96-well plates are incubated at 37° C. in a 7% CO₂ atmosphere with 100% humidity.

Seven days after the fusion, the media should be removed and replaced with IMDM containing 10% FBS, 2 mM L-glutamine, 0.6% 2-mercaptoethanol stock (0.04%), hypoxanthine and thymidine.

Hybridoma Expansion Protocol.

Fourteen days after fusion, the supernatant may be taken from wells with growing hybridoma colonies. The volume of supernatant in each well may be approximately 150-200 microliters. This supernatant may be tested for IgG1 isotype producing hybridomas with specificity for SpA using ELISA as described herein.

Positive hybridoma colonies may be transferred from the 96-well plate to a 24-well plate and 1.8 mL of IMDM containing 20% FBS, 10% Origen Cloning Factor, 2 mM L-glutamine and 0.6% 2-mercaptoethanol stock (0.04%) is added to each well. The 24-well plates are incubated as described for the 96-well plates above. Five days later, the supernatant from 24-well plate should be tested to confirm the presence of specific antibody.

Cells from positive wells may be expanded in T-25 and T-75 flasks (Corning Flasks, Corning, N.Y.). Five vials (1 mL each) of the cells from T-75 flasks are frozen in liquid nitrogen. Cells from positive wells can be cloned by limiting dilution, i.e., hybridoma cells are plated onto 96-well plates at a density of 0.25 cells per well. Growing colonies may be tested 10-14 days later using the same assay that was used to initially select the hybridomas. The subcloned cells are expanded to 24-well plates and, subsequently, T-25, T-75 and T-162 flasks. Vials of subclone cells are frozen as described above.

Sequencing of monoclonal antibodies: Total RNA samples from hybridoma cells were isolated using a standardized protocol. Briefly, 1.4×10⁷ hybridoma cells cultured in DMEM-10 medium with 10% fetal bovine serum (FBS) were washed with PBS, sedimented by centrifugation, and lysed in TRIzol (Invitrogen). Samples were mixed with 20% chloroform and incubated at room temperature for 3 min and centrifuged at 10,000×g for 15 min at 4° C. RNAs in the aqueous layer were removed and washed with 70% isopropanol. RNA was sedimented by centrifugation and washed with 75% diethylpyrocarbonate (DEPC)-ethanol. Pellets were dried and RNA dissolved in DEPC. cDNA was synthesized with the cDNA synthesis kit (Novagen) and PCR amplified using the PCR reagent system (Stratagene), independent primers (5 pmol each), and a mouse variable heavy and light chain-specific primer set (Novagen). PCR products were sequenced and analyzed using IMGT/VQUEST (http://www.imgt.org/IMGT_vquest/share/textes/).

Example 4: Generation of Chimeric and Humanized Anti-Microbial IgG1 Antibodies

Anti SpA Antibodies:

In one example, a chimeric parental version of the murine SPA27 antibody was constructed using the murine variable domain sequences as published in patent application WO 208/140487 A2. The murine variable heavy chain (VH chimeric (SEQ ID NO: 1)) was combined with a human IgG1 heavy chain constant sequence of allotype G1m17 (SEQ ID 30). IgG1 allotype G1m17,1,2 has been used as the reference. The allotypic amino acid positions that include a residue substitution relative to the reference sequence are shown Bold underlined in SEQ ID 30. The heavy chain amino acid sequence of the resulting chimeric antibody is shown in HC 1 (SEQ ID NO: 19). Likewise, the murine variable light chain sequence (VL chimeric (SEQ ID NO: 6)) was combined with a Kappa light chain constant region of allotype Km3, resulting in a chimeric light chain amino acid sequence as shown in LC 1 (SEQ ID NO:21). Heavy chain constant region variant antibodies were constructed as described above for parental antibodies. Following codon optimization for mammalian expression, DNA encoding a Kozak sequence, an N-terminal leader secretion sequence and the target polypeptides was synthesized, cloned into a mammalian expression vector pTT5, and expressed in HEK 293 cells using methods well known in the art (described later).

CDR Grafting and Humanization of Chimeric Antibodies:

CDR grafting can be used to humanize murine antibodies using standard molecular biology techniques known in the art. In one example CDR grafting was used to humanize anti-SpA murine antibody sequences using standard molecular biology techniques known in the art. Such grafted antibodies sequences (humanized) will generally require additional affinity maturation to arrive at a therapeutic humanized antibody of sufficient affinity. Standard methodology known to those practicing the art can be used for both CRD grafting and affinity maturation. One example is the mouse HC and LC CDR sequences from DNA encoding the anti-SpA monoclonal antibody SPA27.

CDRs were grafted into a human IgG1 heavy chain and a Kappa light antibody backbone sequences. The selection of the variable domain human germ line sequence used for grafting is determined by the closest homology to the mouse hybridoma variable domain sequence. In some cases, different VH germ line sequences can be used for each FW region. In the case of SPA-27, the closest heavy chain matches are VH3-49 and VH3-72. Variable heavy chain sequences were combined with constant heavy chain sequences from human IgG1 or its variants. Heavy chain constant region variants which do not bind SpA are used for screening chimeric, CDR grafted and affinity mutated antibodies so as to avoid SpA-Fc binding in ELISA assays, and to allow binding measurements using ELISA, BIACore or DLS (Dynamic Light Scattering).

Design and Construction of Humanized Antibodies Using the Murine SPA27 Anti-SpA Antibody Variable Region Sequence:

Using the anti-SPA27 murine monoclonal antibody as a reference, anti-SPA antibodies were designed using CDR grafting technology. The grafted CDR regions of the variable domains were then combined with light and heavy chain variant human IgG1 constant regions sequences.

The sequences of the heavy and light chain variable regions of SPA-27 were compared to human germline databases and homologous sequences were identified. CDR grafted human Antibody sequences (SEQ ID #1-16) were initially designed. CDR grafted antibodies comprise target variable regions derived from either VH3-49, VH3-72 or VH3-70 human germ line antibody sequences. In an alternative approach, CDR grafted antibodies can comprise a mixture of sequences derived from VH3-49, VH3-72 or VH3-70. A summary of the CDR grafted Human Antibodies derived from SPA-27 are given below.

Heavy Chain Variable Domain.

A Summary of the CDR grafted antibodies sequences are given below. The sequence for each variable heavy chain region is given:

VH chimeric (SEQ ID NO: 1) EVKLVESGGGLVQPGGSRRLSCTTSGFTFTESFMTWVRQPPGKALDWLAF IRNKANGYTTEYSASVKGRFTIARDNSQSILYLQMNALRAEDSATYYCVR GGEYPLYVMDYWGKGTSVTVSS VH1 (SEQ ID NO: 2): EVQLVESGGGLVQPGRSLRLSCTASGFTFTESFMSWFRQAPGKGLEWVGF IRNKANGYTTEYAASVKGRFTISRDDSKSIAYLQMNSLKTEDTAVYYCVR GGEYPLYVMDYWGQGTLVTVSS VH2(SEQ ID NO: 3): EVQLVESGGGLVQPGRSLRLSCTASGFTFTESFMSWIRQPPGKALEWLAF IRNKANGYTTEYAASVKGRFTISRDDSKSIAYLQMNSLKTEDTAVYYCVR GGEYPLYVMDYWGQGTLVTVSS VH3(SEQ ID NO: 4): EVQLVESGGGLVQPGGSLRLSCAASGFTFTESFMDVWRQAPGKGLEWVGR IRNKANGYTTEYAASVKGRFTISRDDSKNSLYLQMNSLKTEDTAVYYCVR GGEYPLYVMDYWGQGTLVTVSS VH4 (SEQ ID NO:5): EVQLVESGGGLVQPGGSLRLSCAASGFTFTESFMDWIRQPPGKALEWLAF IRNKANGYTTEYAASVKGRFTISRDDSKNSLYLQMNSLKTEDTAVYYCVR GGEYPLYVMDYWGQGTLVTVSS

Light Chains.

A Summary of the CDR grafted antibodies is given below. The sequence for each variable light chain region is given:

VL chimeric (SEQ ID NO: 6): DIVLTQSPVSLAVSLGQRATISCRASESVEYYDTSLMQVVYQQKPGQPPK LLIYAASNVESGVPARFSGSGSGTDFSLNIHPVEEDDFATYFCQQSRKVP WTFGGGTKLEIK VL1 (SEQ ID NO: 7): DIVMTQSPDSLAVSLGERATINCKSSESVEYYDTSLLAVVYQQKPGQPPK LLIYAASNVESGVPDRFSGSGSGTDFTLTISSLQAEDVAVYYCQQSRKVP WTFGQGTKLEIK VL2 (SEQ ID NO: 8): DIVMTQSPDSLAVSLGERATINCKSSESVEYYDTSLLAVVYQQKPGQPPK LLIYAASNVESGVPARFSGSGSGTDFTLTISSLQEEDVAVYYCQQSRKVP WTFGQGTKLEIK VL3 (SEQ ID NO: 9): DIVMTQSPDSLAVSLGERATINCKSSESVEYYDTSLLAVVYQQKPGQPPK LLIYAASNVESGVPSRFSGSGSGTDFTLTISSLQPEDVAVYYCQQSRKVP WTFGQGTKLEIK VL4 (SEQ ID NO: 10): DIVMTQSPDSLAVSLGERATINCKSSESVEYYDTSLLAVVYQQKPGQPPK LLIYAASNVESGVPARFSGSGSGTDFTLTISSLQPEDVAVYYCQQSRKVP WTFGQGTKLEIK VL5 (SEQ ID NO: 11): DIVMTQSPDSLAVSLGERATINCRASESVEYYDTSLMQVVYQQKPGQPPK LLIYAASNVESGVPDRFSGSGSGTDFTLTISSLQAEDVAVYYCQQSRKVP WTFGQGTKLEIK VL6 (SEQ ID NO: 12): DIVMTQSPDSLAVSLGERATINCRASESVEYYDTSLMQVVYQQKPGQPPK LLIYAASNVESGVPARFSGSGSGTDFTLTISSLQEEDVAVYYCQQSRKVP WTFGQGTKLEIK VL7 (SEQ ID NO: 13): DIVMTQSPDSLAVSLGERATINCRASESVEYYDTSLMQVVYQQKPGQPPK LLIYAASNVESGVPSRFSGSGSGTDFTLTISSLQEEDVAVYYCQQSRKVP WTFGQGTKLEIK VL8 (SEQ ID NO: 14): DIVMTQSPDSLAVSLGERATINCRASESVEYYDTSLMQVVYQQKPGQPPK LLIYAASNVESGVPARFSGSGSGTDFTLTISSLQPEDVAVYYCQQSRKVP WTFGQGTKLEIK VL9 (SEQ ID NO: 15): DIVMTQSPDSLAVSLGERATINCRASESVEYYDTSLMQVVYQQKPGQPPK LLIYAASNVESGVPDRFSGSGSGTDFTLTISSLQEEDFATYFCQQSRKVP WTFGQGTKLEIK VL10 (SEQ ID NO: 16): DIVMTQSPDSLAVSLGERATINCRASESVEYYDTSLMQVVYQQKPGQPPK LLIYAASNVESGVPARFSGSGSGTDFTLTISSLQEEDFATYFCQQSRKVP WTFGQGTKLEIK VL11 (SEQ ID NO: 17): DIVMTQSPDSLAVSLGERATINCRASESVEYYDTSLMQVVYQQKPGQPPK LLIYAASNVESGVPSRFSGSGSGTDFTLTISSLQEEDFATYFCQQSRKVP WTFGQGTKLEIK VL12 (SEQ ID NO: 18): DIVMTQSPDSLAVSLGERATINCRASESVEYYDTSLMQVVYQQKPGQPPK LLIYAASNVESGVPARFSGSGSGTDFTLTISSLQPEDFATYFCQQSRKVP WTFGQGTKLEIK

The humanized variable heavy chain sequences (SEQ ID NO:2-5)) were combined with a human IgG1 heavy chain constant sequence of allotype G1m17 (SEQ ID NO:30) to generate a humanized heavy chain sequence. Likewise, the humanized light chain sequences (SEQ ID NO:7-18) were combined with a Kappa light chain constant region of allotype Km3, resulting in humanized light chain amino acid sequences. Heavy chain constant region variant antibodies were designed and constructed as described above for parental antibodies. Following codon optimization for mammalian expression, DNA encoding a Kozak sequence, an N-terminal leader secretion sequence and the target polypeptides was synthesized, cloned into a mammalian expression vector pTT5, and expressed in HEK 293 cells using methods well known in the art (described later).

Anti SpA Example Antibodies:

An anti SpA chimeric parental antibody was constructed as follows. The murine variable heavy chain (VH chimeric (SEQ ID NO:1)) was combined with a human IgG1 heavy chain constant sequence of allotype G1m17 (SEQ ID NO:30). The heavy chain amino acid sequence of the resulting chimeric antibody is shown in HC 1 (SEQ ID NO:19). Likewise, the murine variable light chain sequence (VL chimeric (SEQ ID NO:6)) was combined with a Kappa light chain constant region of allotype Km3, resulting in a chimeric light chain amino acid sequence as shown in LC 1 (SEQ ID NO:21). Heavy chain constant region variant antibodies were constructed as described above for parental antibodies. In one example a heavy chain constant region variant (SEQ ID NO:40) constructed. Antibody and their variants were expressed as essentially as follows: Following codon optimization for mammalian expression, DNA encoding a Kozak sequence, an N-terminal leader secretion sequence and the target polypeptides was synthesized, cloned into a mammalian expression vector pTT5, and expressed in HEK 293 cells using methods well known in the art (described later).

Anti-ClfA Antibodies:

A humanized version of the anti-ClfA antibody T1-2 (Domanski et al., 2005) was constructed using the variable domain sequences as published in patent application U.S. 69/794,4662. A parental control antibody sequence was generated as follows: The variable heavy chain from antibody T1-2 (SEQ ID NO:28) was combined with a human IgG1 heavy chain constant sequence of allotype G1m17 (SEQ ID NO:30). The heavy chain amino acid sequence of the resulting antibody is shown in HC 5 (SEQ ID NO: 25. Likewise, the variable light chain sequence (VL chimeric (SEQ ID NO: 29)) was combined with the a Kappa light chain constant region of allotype Km3, resulting in a chimeric light chain amino acid sequence as shown in LC 2 (SEQ ID NO:24). Heavy chain constant region variant antibodies were designed and constructed as described above for parental antibodies. In one example a heavy chain constant region variant (SEQ ID NO:40) constructed. Antibody and their variants were expressed as essentially as follows: Following codon optimization for mammalian expression, DNA encoding a Kozak sequence, an N-terminal leader secretion sequence and the target polypeptides was synthesized, cloned into a mammalian expression vector pTT5, and expressed in HEK 293 cells using methods well known in the art (described later).

Anti-RSV Control Antibodies:

A parental humanized anti-RSV antibody derived from Palivizumab (Synagis, Medimmune Inc) has been used as a heavy chain constant region control antibody (parental polypeptide sequence is shown in SEQ 22). The anti-RSV parental antibody and its heavy chain constant region variants allow the effects of variants to be studies in the absence of target microbe binding by the antigen binding variable domain. The parental humanized anti-RSV heavy chain variable domain was combined with a human IgG1 heavy chain constant region of allotype G1m17 resulting in an amino acid sequence HC3 (SEQ ID NO:22). Likewise, the anti-RSV variable light chain was combined with a Kappa light chain constant region of allotype Km3, resulting in a chimeric light chain amino acid sequence of LC 2 (SEQ ID NO:24). Heavy chain constant region variant antibodies were designed and constructed as described above for parental antibodies. In one example a heavy chain constant region variant (SEQ ID NO:40) constructed. Antibody and their variants were expressed as essentially as follows: Following codon optimization for mammalian expression, DNA encoding a Kozak sequence, an N-terminal leader secretion sequence and the target polypeptides was synthesized, cloned into a mammalian expression vector pTT5, and expressed in HEK 293 cells using methods well known in the art (described later).

Generation of Heavy Chain Constant Region Antibodies and their Variants Example 5: Anti-Microbial Heavy Chain Constant Region Variants

Parental and heavy chain constant region variant anti-SpA, anti-Clfa and anti-RSV antibodies were constructed as described above for parental antibodies. In such variant antibodies, the heavy chain constant region of the variant antibody, contains a heavy chain constant regions including an amino acid sequences selected from the group SEQ ID NO:31-56 (Heavy chain constant region 2-27).

In one example a parental chimeric anti-SpA antibody and an example heavy chain constant region variant (SEQ ID NO: 40) antibody were expressed, purified and characterized: Shown are the amino acid sequence of an anti-SpA parental heavy chain (SEQ ID NO: 19), a variant heavy chain (SEQ ID NO: 20) and a common light chain (SEQ ID NO: 21). Amino acid differences between the parental antibody of allotype G1m17 and an example variant heavy chain content chain amino acid sequence are shown in Bold underlined:

HC 1 Anti SpA Chimeric HC G1M17 (SEQ ID NO: 19) EVKLVESGGGLVQPGGSRRLSCTTSGFTFTESFMTWVRQPPGKALDWLAF IRNKANGYTTEYSASVKGRFTIARDNSQSILYLQMNALRAEDSATYYCVR GGEYPLYVMDYWGKGTSVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCL VKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGT QTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPP KPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREE QYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPR EPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTT PPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLS PGK HC 2 Anti SpA Chimeric variant HC G1M17 (SEQ ID NO: 20) EVKLVESGGGLVQPGGSRRLSCTTSGFTFTESFMTWVRQPPGKALDWLAF IRNKANGYTTEYSASVKGRFTIARDNSQSILYLQMNALRAEDSATYYCVR GGEYPLYVMDYWGKGTSVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCL VKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGT QTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPP KPKDTLMISRTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREE QYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPR EPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTT PPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHN RF TQKSLSLS PGK LC 1 Anti SpA Chimeric LC (SEQ ID NO: 21) KM3DIVLTQSPVSLAVSLGQRATISCRASESVEYYDTSLMQWYQQKPGQP PKLLIYAASNVESGVPARFSGSGSGTDFSLNIHPVEEDDFATYFCQQSRK VPWTFGGGTKLEIKRTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPRE AKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYA CEVTHQGLSSPVTKSFNRGEC

As control antibodies, a humanized RSV variable domain has been used, derived from Palivizumab (Synagis, Medimmune Inc). This anti-RSV variable domain allows the effects of heavy chain constant region variants to be studies in the absence of S. aureus antigen binding by the variable domain. In one example a parental anti-RSV antibodies and an example heavy chain constant region variant (SEQ ID NO:40) were characterized: Shown are the amino acid sequence of an anti-RSV parental heavy chain (SEQ ID NO:22), an example variant heavy chain (SEQ ID NO:23) and a common light chain (SEQ ID NO:24). Amino acid differences between the parental antibody of allotype G1m17 and an example variant heavy chain content chain amino acid sequence are shown in bold underlined:

HC3 Anti RSV HC parental IgG1 of allotype G1m17 (SEQ ID NO: 22) QVTLRESGPALVKPTQTLTLTCTFSGFSLSTAGMSVGWIRQPPGKALEWL ADIWWDDKKHYNPSLKDRLTISKDTSKNQVVLKVTNMDPADTATYYCARD MIFNFYFDVWGQGTTVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCLVK DYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQT YICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKP KDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYN STYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQ VYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPV LDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK HC4 Anti RSV variant HC of allotype G1m17 (SEQ ID NO: 23) QVTLRESGPALVKPTQTLTLTCTFSGFSLSTAGMSVGWIRQPPGKALEWL ADIWWDDKKHYNPSLKDRLTISKDTSKNQVVLKVTNMDPADTATYYCARD MIFNYFDVWGQGTTVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCLVKD YFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTY ICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPK DTLMISRTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREEQYNS TYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQV YTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVL DSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHN RF TQKSLSLSPGK LC 2 Anti RSV LC (SEQ ID NO: 24) DIQMTQSPSTLSASVGDRVTITCSASSRVGYMHWYQQKPGKAPKLLIYDT SKLASGVPSRFSGSGSGTEFTLTISSLQPDDFATYYCFQGSGYPFTFGGG TKLEIKRTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVD NALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGL SSPVTKSFNRGEC

In an additional example a humanized anti-ClfA antibody and an example heavy chain constant region variant (SEQ ID NO: 40) were characterized. Shown are the amino acid sequence of an anti-ClfA parental heavy chain (SEQ ID NO: 25) an example variant heavy chain (SEQ ID NO:26) and a common light chain (SEQ ID NO:27). Also shown are the variable heavy and Light chain sequences used in parental and variant antibodies (SEQ ID NO:28 and SEQ ID NO:29). Amino acid differences between the parental antibody of allotype G1m17 and an example variant heavy chain content chain amino acid sequence are shown in Bold underlined:

HC 5 Humanized anti-ClfA HC in G1m17 heavy chain background (SEQ ID NO: 25) QVQLKESGPGLVKPSQTLSITCTISGFSLSRYSVHWVRQPPGKGLEWLGM IWGGGNTDYNSALKSRLSISKDNSKNQVFLKMNSLTAADTAVYYCARKGE FYYGYDGFVYWGQGTLVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCLV KDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQ TYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPK PKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQY NSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREP QVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPP VLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPG K HC 6 Humanized anti-ClfA HC in variant G1M17 heavy  chain background (SEQ ID NO: 26) QVQLKESGPGLVKPSQTLSITCTISGFSLSRYSVHWVRQPPGKGLEWLGM IWGGGNTDYNSALKSRLSISKDNSKNQVFLKMNSLTAADTAVYYCARKGE FYYGYDGFVYWGQGTLVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCLV KDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQ TYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPK PKDTLMISRTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREEQY NSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREP QVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPP VLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHN RF TQKSLSLSPG K LC 3 Humanized ClfA LC KM3 (SEQ ID NO: 27) DIVMTQSPDSLAVSLGERVTMNCKSSQSVLYSSNQKNYLAWYQQKPGQSP KLLIYWASTRESGVPDRFSGSGSGTDFTLTISSVQAEDLAVYYCHQYLSS YTFGGGTKLEIKRTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAK VQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACE VTHQGLSSPVTKSFNRGEC

Heavy Chain and light chain variable domain sequenced of the example humanized anti-ClfA antibody.

VH 5 (SEQ ID NO: 28): ClfA Humanized 12-9 VH sequence QVQLKESGPGLVKPSQTLSITCTISGFSLSRYSVHWVRQPPGKGLEWLGM IWGGGNTDYNSALKSRLSISKDNSKNQVFLKMNSLTAADTAVYYCARKGE FYYGYDGFVYWGQGTLVTVSS VL 13 (SEQ ID NO: 29): ClfA Humanized 12-9 VL sequence DIVMTQSPDSLAVSLGERVTMNCKSSQSVLYSSNQKNYLAWYQQKPGQSP KLLIYWASTRESGVPDRFSGSGSGTDFTLTISSVQAEDLAVYYCHQYLSS YTFGGGTKLEIK Example Variant IgG1 Constant Region Sequences:

Modeling was used to investigate Immunoglobulin heavy chain constant region interactions with a number of microbial IgBPs including SpA, Sbi, SSL10 and Protein G. Amino acids were selected from modeling studies for substitution in variant heavy chain constant region.

In claimed embodiments, the heavy chain constant region variant antibody is of IgG immunoglobulin, in which at least one amino acid from the heavy chain constant region selected from the group consisting of amino acid residues 214, 251, 252, 253, 254, 274, 276, 311, 314, 356, 358, 380, 382, 384, 419, 422, 428, 431, 432, 433, 434, 435, 436 and 438 (EU numbering) is substituted with an amino acid residue different from that present in the unmodified IgG1 antibody.

The amino acid sequence of example variant IgG1 heavy chains that attenuate the binding to one or more microbial IgBPs are shown below in sequences SEQ ID NO: 31-56). The Heavy chain constant region is shown using the one letter amino acid code (EU numbering 118-447). X denotes variable heavy chain residues. In different immunoglobulins described herein, the number of variable domain residues in the heavy chain variable region may vary, where the number of X residues can be greater or less than shown in HCl-HC-27. With respect to Variant Heavy Chain Fc Region Sequences, the amino acid positions that include a residue substitution relative to the reference sequence of allotype G1m17,1,2 are underlined. E356, M358 and A431 represent allotypic substitutions relative to the allotype G1m17,1,2 reference sequence (D365, L358, G431).

Heavy chain constant region 1 (SEQ ID NO: 30) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHE A LHNHYTQKSLSLSPGK Heavy chain constant region 2 (SEQ ID NO: 31) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHE A LHN R YTQKSLSLSPGK Heavy chain constant region 3 (SEQ ID NO: 32) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHE A LHN R YTQKSLSLSPGK Heavy chain constant region 4 (SEQ ID NO: 33) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGN I FSCSVMHE A LHN R YTQKSLSLSPGK Heavy chain constant region 5: (SEQ ID NO: 34) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGN I FSCSVMHE A LHN R YTQKSLSLSPGK Heavy chain constant region 6: (SEQ ID NO: 35) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQ E GNVFSCSVMHE A LHN R YTQKSLSLSPGK Heavy chain constant region 7 (SEQ ID NO: 36) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQ E GNVFSCSVMHE A LHN R YTQKSLSLSPGK Heavy chain constant region 8: (SEQ ID NO: 37) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQ E GN I FSCSVMHE A LHN R YTQKSLSLSPGK Heavy chain constant region 9: (SEQ ID NO: 38) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQ E GN I FSCSVMHE A LHN R YTQKSLSLSPGK Heavy chain constant region 10: (SEQ ID NO: 39) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHE A LHN RF TQKSLSLSPGK Heavy chain constant region 11: (SEQ ID NO: 40) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX   XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHE A LHN RF TQKSLSLSPGK Heavy chain constant region 12: (SEQ ID NO: 41) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGN I FSCSVMHE A LHN RF TQKSLSLSPGK Heavy chain constant region 13: (SEQ ID NO: 42) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGN I FSCSVMHE A LHN RF TQKSLSLSPGK Heavy chain constant region 14: (SEQ ID NO: 43) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQ E GNVFSCSVMHE A LHN RF TQKSLSLSPGK Heavy chain constant region 15: (SEQ ID NO: 44) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQ E GNVFSCSVMHE A LHN RF TQKSLSLSPGK Heavy chain constant region 16: (SEQ ID NO: 45) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQ E GN I FSCSVMHE A LHN RF TQKSLSLSPGK Heavy chain constant region 17: (SEQ ID NO: 46) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQ E GN I FSCSVMHE A LHN RF TQKSLSLSPGK Heavy chain constant region 18: (SEQ ID NO: 47) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHE A LHNH F TQKSLSLSPGK Heavy chain constant region 19: (SEQ ID NO: 48) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMISRTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHE A LHNH F TQKSLSLSPGK Heavy chain constant region 20: (SEQ ID NO: 49) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMI T RTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHE A LHNHYTQKSLSLSPGK Heavy chain constant region 21: (SEQ ID NO: 50) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMI T RTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHE A LHNHYTQKSLSLSPGK Heavy chain constant region 22: (SEQ ID NO: 51) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT L T I T RTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHE A LHNHYTQKSLSLSPGK Heavy chain constant region 23: (SEQ ID NO: 52) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT L T I T RTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHE A LHNHYTQKSLSLSPGK Heavy chain constant region 24: (SEQ ID NO: 53) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMI T RTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHE A LHNH F TQKSLSLSPGK Heavy chain constant region 25: (SEQ ID NO: 54) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT LMI T RTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHE A LHNH F TQKSLSLSPGK Heavy chain constant region 26: (SEQ ID NO: 55) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT L T I T RTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHE A LHNH F TQKSLSLSPGK Heavy chain constant region 27: (SEQ ID NO: 56) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYF PEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYIC NVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDT L T I T RTPEVTCVVVDVSHEDPEV Q FNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYT LPPSR E E M TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHE A LHNH F TQKSLSLSPGK

Example parental and heavy chain constant region variants have amino acid sequences shown in SEQ ID 30-56.

In examples, parental heavy chain variable domains were combined with a human IgG1 heavy chain constant region of allotype G1m17 resulting in an heavy chain constant region amino acid sequence of SEQ ID NO:30. Likewise, variable light chains were combined with a Kappa light chain constant region of allotype Km3). Following codon optimization for mammalian expression, DNA encoding a Kozak sequence, an N-terminal leader secretion sequence and the target polypeptides was synthesized, cloned into a mammalian expression vector pTT5, and expressed in HEK 293 cells using methods well known in the art (described later).

Construction, Expression, Purification of Antibodies and their Variants

Example 6: Expression and Purification of Antibodies and their Variants

Antibodies and their heavy chain constant region variants were produced as follows: Codon optimization for antibody expression in 293 cells was performed using the OptimumGene™ Gene Design Technology (GenScript USA Inc). DNA was synthesized including a 5′ EcoR1 cloning site, a Kozak sequence, and a leader signal sequence, followed by the IgG heavy or light chain DNA sequence. The 3′ end of the Ig DNA sequences are followed by a stop codon and HindIII cloning site. One Synthetic DNA examples is given in SEQ ID: 57, where XXXXXXXXXXXX represents the codon optimized heavy or light chain DNA sequence). Oligonucleotide synthesis was performed using methods that are well known in the art. Antibody heavy and light chain synthetic DNA sequences were cloned into the pUC57 vector using EcoR1 and Hind III cleavage sites. Plasmid preparations were made of each plasmid and the immunoglobulin sequence inserts were sub-cloned into the expression vector pTT5 (National Research Council of Canada (NRCC)). Plasmid preparations of immunoglobulin expression vectors were made to provide transfection grade expression plasmids.

EcoR1 Kozak Sequence Leader signal peptide SEQ ID: 57 GAATT CGCCGCC ACCATGGGATGGAGCTGTATCATCCTCTTCTTGGTAGCAACAG CTACAGGTGTCCACTCCXXXXXXXXXXXXTGA TAAGCTT                                    Stop codon Hind III

Expression and Purification of Antibodies by Protein A or Protein G Chromatography:

Recombinant plasmids encoding the heavy chain and light chain of anti-microbial antibodies, or their heavy chain constant region variants, were transiently co-transfected into 100 mL of suspension HEK293 cell cultures, respectively. Following confirmation of antibody expression, large scale HEK293 expression of antibodies was performed in bioreactors to provide 50 mg quantities of test antibodies.

HEK 293-6E cells were grown in serum free Freestyle 293 expression medium (Invitrogen, Carlsbad, Calif., USA). The cells were maintained in Erlenmeyer Flasks at 37° C. with 5% CO2 (Corning Inc., Acton, Mass.) on an orbital shaker (VWR Scientific, Chester, Pa.). One day before transfection, the cells were seeded at an appropriate density in Corning Erlenmeyer Flasks. On the day of transfection, DNA and PEI (Polysciences, Eppelheim, Germany) were mixed at an optimal ratio and then added into the flask with cells ready for transfection. The supernatant collected on day 6 was used for purification.

Cell culture broth was centrifuged and followed by filtration. Filtered supernatant was loaded onto a 5 mL HiTrap™ Protein G HP or HiTrap™ rProtein A FF column (GE Healthcare, Uppsala, Sweden) at 1.0 mL/min. After washing and elution with appropriate buffer (The following buffers were used affinity chromatography: Binding buffer: 20 mM PB, 150 mM NaCl, pH 7.2; Elution buffer: 50 mM citrate (pH 3.0) or 0.1M Gly-HCl (pH 3.0); Neutral buffer: 1 M Tris-HCl, pH 9.0), the fractions were collected and neutralized with 1M Tris-HCl, pH 9.0. The purified protein was analyzed by SDS-PAGE Western blot by using standard protocols for molecular weight, yield and purity measurements.

Results of Expression and Purification:

As expected the anti-RSV heavy chain constant region variant (MAB5) was not bound by HiTrap™ rProtein A FF column. This finding confirms that SpA no longer binds to the variant heavy chain constant region sequence (SEQ ID: 40). MAB5 was bound by the HiTrap™ Protein G HP column, demonstrating that although SpA and G both bind the CH2-CH3 interface of IgG1, their binding involves different amino acids. Therefore, His 435 and Tyr 436 are not required for binding to Protein G, as they have been mutated to Arg 435 and Phe 436 In the variant antibody MAB5. Thus, variant antibodies having a heavy chain constant region amino acid sequence of SEQ ID: 40 do not bind to SpA via their Fc domain, but do bind to Protein G. Such antibodies can be affinity purified by Protein G affinity chromatography. This finding was surprising as Tyr436 makes important interactions with Protein G. This finding is important for the efficient purification of variant antibodies having a variant heavy chain constant region containing Arg 435 and Phe 436 (all amino acids are according to EU numbering).

Both the parental anti-SpA antibody and its variant were purified by affinity chromatography on a HiTrap™ rProtein A FF column. Although the anti-SpA variant (MAB2) does not bind to SpA via its Fc domain (see later; FIG. 22-26 and text), the antibody does bind SpA via its variable domain. The purification of antibody MAB2 thus represents SpA binding via the variable domain of the antibody. The anti-SpA parental antibody (MAB1) can bind SpA via its Fc and variable domains.

Both the anti-ClfA parental antibody and its variant were purified by affinity chromatography on Protein G. As was demonstrated for the anti-RSV variant antibody (MAB5), the anti-ClfA variant antibody (MAB4) also bind via its Fc domain to Protein G but not SpA. The parental anti-ClfA was bound by both SpA and Protein G and was purified by Protein G affinity chromatography.

Characterization of Example Antibodies:

Purified antibodies were analyzed by SDS-PAGE and Western blotting. For western blotting, the primary antibody was Goat-anti-Human IgG-HRP (GenScript, Cat.No:A00166).

SDS-PAGE and Western Blotting of Anti-SpA Parental Antibody MAB1 and Variant Antibody MAB2.

Anti-SpA parental antibody MAB1 (HC amino acid SEQ ID NO:19 and LC amino acid SEQ ID NO: 21) and an example anti-SpA variant antibody MAB2 (HC amino acid SEQ ID NO:20 and LC amino acid SEQ ID NO: 21) were expressed in HEK293 cell, purified on HiTrap™ rProtein A FF, and analyzed by SDS-PAFGE and western blotting (FIG. 16).

SDS-PAGE and Western blotting of anti-Clfa parental antibody MAB3 and variant antibody MAB4.

Anti-ClfA parental antibody MAB3 (HC amino acid SEQ ID NO:25 and LC amino acid SEQ ID NO: 27) and an example anti-ClfA variant antibody MAB4 (HC amino acid SEQ ID NO:26 and LC amino acid SEQ ID NO: 27) were expressed in HEK293 cell, purified on Protein G, analyzed by SDS-PAGE and western blotting (FIG. 17).

Anti-RSV Control Variant Antibody (MAB5)

Anti-RSV variant antibody MAB5 (HC amino acid SEQ ID NO:23 and LC amino acid SEQ ID NO: 24) were expressed in HEK293 cell, purified on Protein G and analyzed by SDS-PAFG (FIG. 18). MAB5 does not bind SpA and was purified on Protein G.

Biological Testing of Example Anti-Microbial Immunoglobulins and their Heavy Chain Constant Region Variants Example 7: Antibody Characterization for Binding to S. aureus IgBP by Immuno-Diffusion

Binding to IgBPs: All procedures should be performed at room temperature unless specified otherwise. Goat anti-mouse antibody (gamma-chain specific, conjugated to horseradish peroxidase (HRP)) can be obtained from Zymed Laboratories (Invitrogen, Inc., Carlsbad, Calif.). TMB (3,3′,5,5′-tetramethylbenzidene), a chromogenic substrate for horseradish peroxidase enzyme activity, may be obtained from Neogen Corporation (Lansing, Mich.). The described procedures can be used for any IgBP. SpA and Sbi are used as illustrative examples. SpA may be purchased from commercial sources or produced using standard molecular Biology methods as previously described. For example, SpA domains A, B, C, D and/or E, or their variants (Kim et al., 2010) can be PCR amplified using two primers. Alternatively, the sequence of the SpA or Sbi domain or domains of interest can be synthesized and expressed using molecular biology techniques well known in the art. PCR products can be cloned into pET-15b to generating N-terminal His6-tagged recombinant fusion proteins. Polyhistidine-tagged fusion proteins can be purified by affinity chromatography. Alternatively, other fusion tags such as GST can be used for expression and purification. Sbi or its IgFc binding domains were produced using standard molecular biology methods as previously described (Haupt et al., 2008; Zhang et al., 1999).

The following IgBPs or their domains have been used to characterize S. aureus IgBP binding to variant and parental heavy chain constant region sequences (immune binding by the variable domain vs Fc binding by the heavy chain constant region).

Expression and Purification of SpA.

Cloning, Expression and Purification of Recombinant Sbi and SpA:

Recombinant fragments of the N-terminal region of Sbi (adjacent to the poly-proline region) are engineered, expressed and purified as His Tagged fusions as described previously by (Burman et al. 2008, THE JOURNAL OF BIOLOGICAL CHEMISTRY VOL. 283, NO. 25, pp. 17579-17593, Jun. 20, 2008). The following Sbi constructs were used in this study: Sbi-E (amino acids 28-266) containing IgG-binding domains I and II and C3 interacting domains III and IV; Sbi-III/IV (amino acids 150-266). Sbi fragments were purified by nickel ion-chelating chromatography. Recombinant SpA can be purchased of produced as described previously (O'Seaghdha et al., 2006).

GST-SPA-D expression: E. coli strain BL21 (DE3) was used for the GST-SpA domain D fusion protein expression (construct provided by Prof Timothy Foster, Trinity College Dublin). Bacteria containing pGEX-KG plasmid was grown overnight in LB medium supplemented with 100 μg/ml ampicillin at 37° C. The 15 ml primary culture was incubated with 1L LB medium containing 100 μg/ml ampicillin. Cells were grown at 37° C. with shaking at 180 rpm. The expression of the GST-SpA domain fusion protein was induced during the exponential phase of growth (OD₆₀₀=0.75) by adding isopropyl thiogalactoside (IPTG) to a final concentration of 0.5 mM in the culture. E. coli cells were collected by centrifugation (8000 g, 20 min) 3 h after induction. Cell pellet was suspended in 20 ml of PBS. The re-suspended cells were sonicated on ice for 6 times at 80% amplitude for 10 s separated by 10 min interval. The resulting extract was clarified by centrifugation (60,000 g, 30 min, 4° C.). The supernatant was collected and purified through affinity chromatography. The supernatant sample was split equally and loaded on a 1 ml GSTrap column (GE healthcare) using AKTA with a flow rate of 1 ml/min. The loaded column was washed with 10 column volumes of PBS buffer and the bound GST-SpA domain D fusion protein was eluted with GST Elution buffer (10 mM glutathione, 50 mM Tris, pH8.0). The peak fractions of the GST-SpA domain D fusion protein was then buffer exchange into PBS buffer for further use.

SSL10 from S. aureus NCTC8325, kind gift from Prof Jos van Strijp and Dr Carla de Haas.

Sbi-E and Sbi-III-IV Expression:

Sbi constructs were expressed in Escherichia coli strains BL21(DE3), BL21(DE3)-Star, or Rosetta (see also Burman et al. JBC 283; 17579-17593, 2008). Freshly transformed E. coli cells were grown in a shaker at 37° C. in Luria Bertani broth (LB), containing ampicillin, until they reached an extinction of 0.6 at 600 nm. Isopropyl-D-thiogalactopyranoside (Melford) was added to a final concentration of 0.2 mM, and the cells were incubated at 28° C. for an additional 4 h. Cells from a 1-liter culture were harvested by centrifugation, resuspended in 10 ml of binding buffer (20 mM Tris-HCl, 0.5 M NaCl, 20 mM imidazole, pH 8.0), and lysed by sonication. The lysate was centrifuged at 40,000 g for 15 min and the supernatant filtered through a 0.45 μm filter. The proteins were purified using nickel-ion chelating chromatography by either applying the filtered supernatant to a Sartobind membrane (Sartorius) or a 1-ml HiTrap column attached to an AKTA purifier (Amersham Biosciences). Next, the column was washed with binding buffer, and the bound proteins were eluted with a buffer containing 1M imidazole, for the Sartobind purification, or a 0.05-1 M imidazole gradient for the HiTrap purification. Purified protein was dialyzed into a buffer solution, typically 20 mM Tris, pH 8.0, 100 mMNaCl, and stored at 80° C. until use.

Double Immunodiffusion Assay:

Double immunodiffusion experiments were performed on Petri dishes containing a 1% agarose gel. Wells were punched in the agar and individual wells filled with 50 μl of sample at 1 mg/ml in PBS (anti-SpA monoclonals; Recombinant SpA (Biovision) GST-SpA-D; Sbi-E, Sbi III-IV or SSL10), and left to incubate for 72 h at 4° C. Insoluble protein complexes formed precipitin lines at the zone of equivalence. Large soluble protein complexes were vizualised by Coomassie staining.

Results: MAB1 (Parental anti-SpA antibody) formed a precipitin Line (after day 1) with SpA and (after day 2) with Sbi-E (fragment of Sbi containing the two Ig-binding domains and two complement binding domains). In contract the anti-RSV variant antibody did not form a precipitin line with either SpA or Sbi-E. As the variable domain of MAB1 recognizes SpA, this result shows that binding to Sbi-E is mediated by Fc binding to the parental antibody, whereas binding to SpA is likely a combination of variable domain and Fc binding. MAB2 (anti-SpA variant example) forms a precipitin line (after day 4) only with SpA. This demonstrated that MAB2, like the control variant antibody MAB5 (anti-RSV variant antibody), does not bind via its Fc domain to Sbi-E or to SpA. The precipitin line formed with SpA represents variable domain binding to SpA.

In a second series of immune-precipitation experiments, MAB1 (parental anti-SpA antibody) formed a precipitin Line with SpA domain D, but not with Sbi III/IV domains, which do not have Fc binding function. In contact no precipitin lines are seen with variant MAB2 (panel A). Following Coomassie staining, a week precipitin line is seen with MAB2 (anti-SpA variant example antibody), which represents variable domain binding to SpA domain D. This indicates that MAB2 forms a small soluble complex with SpA domain D, which is only visible with Coomassie staining of the ID plate. The data show that MAB2, in contract to MAB1, does not precipitate in the presence of the single SpA domain, but forms a soluble complex as evidenced by coomassie staining of the immunodiffusion gel. This data is consistent with the design objective of the variant antibody, which has abolished the SpA and Sbi Fc binding sites from the heavy chain constant region of the anti-SpA variant antibody (MAB2) and the anti-RSV variant antibody (MAB5).

Example 8: Antibody Characterization for Binding to S. aureus IgBP by Dynamic Light Scattering (DLS)

Dynamic light scattering is a technique for measuring the size of molecules and nanoparticles. Scattering intensity is proportional to the square of the protein molecular weight, making the technique ideal for identifying the presence of antibody antigen complexes and aggregates. DLS was used to investigate antibody antigen complex formation.

Immune complex formation was characterised by dynamic light scattering (Nano-S Zetasizer, Malvern). All readings were taken at 25° C. over a three consecutive 40-second periods in a low-volume, sealed quartz cuvette containing 50 μl samples of the anti-SPA monoclonal antibodies (1 mg/ml) and mixtures with (1 mg/ml) recombinant 4-domain SpA (Biovision); GST-SpA-D; Sbi-E, Sbi III-IV or SSL10.

FIG. 22 shows the DLS results for the control anti-RSV antibody (MAB5). The left panel shown the analysis of the control anti-RSV variant antibody alone (MAB5). The right panels show the size distribution in the presence of either Sbi-E (fragment of Sbi containing the two Ig-binding domains and two complement binding domains) or SpA1-4 (SpA IgBP domains 1-4). There is no peak shift seen by DLS, indicate no immune complexes have been formed between the variant antibody and the Sbi or SpA IgBP domains. These results are in agreement with the lack of precipitin lines in ID experiments.

In contract to the variant anti-RSV antibody, the parental anti-SpA antibody (MAB1) shows a large complex pattern of peak shifts in the presence of SpA 1-4, indicating large antibody-SpA complexes and cross-linking (FIG. 23—upper right panel)). This also occurs with Sbi-E, although the major peak shift appears relatively homogeneous, and large complexes are less apparent (Lower right panel-blue circle). No peak shifts were seen with SbiIII/IV (lower right panel), demonstrating that the interaction with Sbi is via antibody Fc interactions with the Sbi FcBP domains present in Sbi-E. This result is in agreement with the results generated by ID studies (FIGS. 20 and 21).

FIG. 24 shows the DLS analysis of the parental anti-SpA antibody (MAB1) with SpA-2 (SpA domain D alone). Peak shift DLS analysis was performed after incubation of antibody and SpA-2 for 1 min (upper right panel) and 10 mins (lower right panel). Complex formation and precipitation are seen to increase rapidly with time (FIG. 24). The results found with MAB1 are in agreement with the results generated by ID studies (FIGS. 20 and 21).

In contract to the parental anti-SpA antibody, the anti-SpA variant antibody (MAB2) shows no peak shift in the presence of Sbi-E, and a small homogeneous peak shift in the presence of SpA 1-4 (FIG. 25). The overlap of the MAB2 control and MAB2 in the presence of SpA 1-4 is shown in the lower left panel of FIG. 25. This result demonstrates that the variant heavy chain constant region of MAB2 does not bind to Sbi or SpA. The complex formation seen with SpA 1-4 represents binding via the variable domain of the anti-SpA variant antibody. Analysis of the single SpA domain D construct (FIG. 26), did not indicate any measurable peak shift due to the small size of the single SpA domain D, and the absence of any cross linking (FIG. 26, lower panel). The ant-SpA variant antibody (MAB2) shows a peak shift with DLS in the presence of SpA that is consistent with a soluble complex formed via the variable domain of the antibody. No cross-linking or precipitation peaks can be observed. The results found with MAB2 are in agreement with the results generated by ID studies (FIGS. 20 and 21).

Example 9: ELISA Binding to Isolated Microbial IgBPs

Such IgBP domains, variants, and IgBP domains from different S. aureus stains having a variety of amino acid substitutions within their IgBP can be used to determine the binding to IgBP domains and full length proteins from different microbial stains. For example, in the case of S. aureus SpA, different domains (for example, the amino acid sequence of SpA from clinical stains shown in FIG. 11 for domains A, D, C, D and E), can be used for binding and epitope mapping of antibodies described herein. The antibodies that may be used in accordance with the embodiments described herein are able to bind to epitopes that block one or more virulence functions of SpA, including Fc binding, VH3 Fab binding vWF binding, TNFR binding, EGFR binding and osteoblast binding. Additional antibodies are able to recognize conserved functional epitopes on SpA domains that allows the antibody to binds to multiple stains of SpA and multiple domains within such stains.

The target antigen (100 μL of 1 μg/mL SpA or Sbi antigens suspension in carbonate buffer, pH 9.2) may be coated in each well of the ELISA plates (Immulon 2; Dynex Technologies, Inc., Chantilly, Va.) for 1 hour at 37° C. After the coating step, the wells are washed twice with PBST (phosphate buffered saline (150 mM NaCl in 10 mM sodium phosphate buffer, pH 7.4) containing 0.05% w/v Tween 20).

After discarding the last wash, coating the wells with the target antigen, nonspecific protein-binding sites in the ELISA plates may be blocked. Two hundred microliters of PBST containing 2% (w/v) dehydrated skim milk (blotto solution) are added to each well. The plates are incubated at 37° C. for 1 hour. The blotto solution should then be discarded. Murine IgG1 antibody or chimeric/humanized antibodies in which H435 of the Fc region has been mutated to R to abolish Fc binding to SpA, (100 μL/well, diluted in wash buffer) may be added to each well. The plates are incubated for 1-2 hours at 37° C. After incubation, wells are washed 3 times with Mild Elution Buffer pH 6.0 (Thermo Scientific cat #21033).

One hundred microliters of an appropriate dilution of Goat anti-mouse or anti-human antibody-HRP conjugate in the blotto solution may be added to each well and incubated at 37° C. for 1-2 hours. After this incubation period, the conjugate solution should be removed and the wells washed 3 times with PBST. After removing the last wash, 100 μL of TMB (Kblue, Neogen Cat No. 300199) can be added to each well and the plates are held at room temperature for 1-10 minutes to observe the development of blue color. The relative HRP enzyme activity in each well is measured in a plate reader by absorbance of a 650-nm wavelength light source.

Example 10: Inhibition of Virulence Functions of SpA by Antibodies and their Variants

Inhibition of S. aureus SpA-Fc binding by anti SpA antibodies: inhibition of binding of human IgG to SpA can be tested by ELISA. ELISA plates are coated with recombinant SpA or individual domains of SpA. Purified SpA or its domains are coated onto ELISA plates in 0.1 M carbonate buffer, pH 9.5. Plates are incubated with peroxidase-conjugated human IgG, (The Jackson Laboratory), or purified labeled human IgG1 Fc and developed using OptEIA reagent. Alternatively, S. aureus cells can be used (see later method for cell ELISA). For inhibition of labeled IgG-Fc binding, plates are incubated with anti SpA antibodies (heavy chain constant region variants are used, which do not bind to SpA via the Fc domain) before ligand binding.

Inhibition of S. aureus SpA-vWF binding by anti SpA antibodies: inhibition of binding of human IgG to SpA can be tested by ELISA. ELISA plates are coated with recombinant SpA or individual domains of SpA. Purified SpA or its variants are coated onto ELISA plates in 0.1 M carbonate buffer, pH 9.5. Plates are incubated with peroxidase-conjugated human vWF, (Thermo Fisher Scientific) and developed using OptEIA reagent. For inhibition of labeled vWF binding, plates are incubated with anti SpA antibodies (heavy chain constant region variants are used, which do not bind to SpA via the Fc domain) before ligand binding.

Inhibition of S. aureus SpA-VH3 binding by anti SpA antibodies: inhibition of binding of human VH3 IgG to SpA can be tested by ELISA. ELISA plates are coated with recombinant SpA or individual domains of SpA. Purified SpA or its variants were coated onto ELISA plates in 0.1 M carbonate buffer, pH 9.5. Plates are incubated with peroxidase-conjugated human Fab VH3, (Graille et al., 2000) and developed using OptEIA reagent. For inhibition of labeled VH3 Fab binding, plates were incubated with anti SpA antibodies (heavy chain constant region variants are used, which do not bind to SpA via the Fc domain) before ligand binding.

Example 11: ELISA Binding to Target Microbes

Binding to S. aureus Cells.

Antibodies and their Fc variants may be tested for their ability to bind to intact cells of S. aureus. The bacterial strains used in this example, S. aureus can be obtained from the American Type Culture Collection (Manassass, Va.).

Bacterial cultures used for antigen preparation may be grown overnight at 37° C. in Tryptic Soy Broth. The cell suspensions are washed three times by centrifuging the suspension at 10,600×g for 10 minutes at 4° C., decanting the supernatant, and resuspending the pellet in 100 mM sodium bicarbonate, pH 9.5. After the final wash, the cells are suspended in the sodium bicarbonate buffer to approximate cell densities of 10⁷′ 10⁶′ and 10⁵ colony-forming units per milliliter. These suspensions can be used as antigen to coat 96-well plates. Control solutions, containing 1.0, 0.1, and 0.01 mg/mL, respectively, purified SpA are coated into several wells of each plate.

Streptavidin-conjugated alkaline phosphatase can be obtained from Jackson Immunoresearch (West Grove, Pa.) and may be diluted to a working concentration of 0.5 μg/mL prior to use. The alkaline phosphatase chromogenic substrate, pNPP, can be obtained from KPL (Gaithersberg, Md.). Anti-SpA monoclonal antibody SPA-27 and its corresponding biotin-conjugated derivative may be obtained from Sigma Chemical Company (St. Louis, Mo.).

Bacterial suspensions and SpA controls may be added to a 96-well plate (100 μg/well) and the plates may be incubated at 37° C. for 1 hour. The wells are then washed five times with PBS. Nonspecific protein-binding sites re blocked by adding 200 L of a blotto solution (PBST with 2% w/v nonfat dehydrated milk) and the plates are held overnight at 4° C. The plates are subsequently washed with PBST.

Unlabeled test antibody solutions may be diluted to 50 μg protein/mL in acetate buffer (500 μM NaCL/100 μM Sodium acetate, pH 3.5). These solutions may be used to prepare serial 2-fold dilutions (to 0.78 μg protein/mL) of the antibodies in acetate buffer. SPA-27 antibody is use as a positive control.

One hundred microliters of each dilution of the murine IgG1 antibodies or chimeric/humanized antibodies of IgG1 isotype (with one or more Fc region mutations designed to block non specific antibody binding to SpA and Sbi) are then transferred into duplicate wells and the plates are incubated at 37° C. for 1 hour. The plates may then be subsequently washed five times with Mild Elution Buffer pH 6.0 (Thermo Scientific cat #21033).

One hundred microliters of the diluted, biotin-conjugated anti mouse or anti human antibody may be added to the wells and the plates are incubated at 37° C. The wells may then be washed with PBST.

After washing the wells, 100 μL of streptavidin-alkaline phosphatase conjugate, diluted in blotto solution, may be added to each well and the plates may be incubated at 37° C. for 1 hour. After washing the wells, 100 μL of the pNPP substrate solution is added to each well and the plates may be held at room temperature for 10 minutes. The alkaline phosphatase reaction may be stopped by adding 100 μL of 5% (w/v) disodium EDTA and the plates may be placed in a plate reader, where the absorbance at 405-nm wavelength is read.

The IgG1 hybridoma supernatants may be diluted in sodium acetate buffer (500 μM NaCL/100 μM Sodium acetate, pH 3.5) for the binding assay. After the binding reaction, the amount of antibody bound to the immobilized bacteria is measured using the alkaline phosphatase-conjugated antibody and detection reagents.

In an alternative method, an ELISA based screen was used to investigate anti-SpA and anti-ClfA antibody binding to S. aureus (Newman stain) and a SpA deficient S. aurues stain (ΔSpA) in the presence and absence of human IgG1-Fc used to block non-specific binding and IgBP medicated Fc binding.

ΔSpA strains of S. aureus can be generated by deletion of the spa gene on the chromosome of S. aureus Newman by allelic replacement, as described previously (Bae T., and Schneewind O. (2005)).

One day before the experiment, 100 μl/well of a Staph aureus overnight culture diluted to an OD600 of 1.0 was added to a 96 well plate and incubated at 4° C. overnight. On the day of the experiment, plates were washed with 150 μl/well PBS-T (PBS with 0.05% Tween 20) 2× then blocked with 150 μl/well PBS-T w/0.5% BSA. The plates were agitated for 1 hour after blocking. The plates were then washed with 150 μl/well PBS-T (2×) then 100 μl/well of primary mAb at various dilutions were added to each ELISA plate. The plate was shaken at room temp for 12 hour, washed with 150 μl/well PBS-T (2×) then 100 μl/well secondary antibody (goat antihuman IgG (HRP) @ 1:5,000 in PBS-T—Thermo #31413) was added. The plates were shaken at room temp for 1 hour, washed with 150 μl/well PBS-T (2×) then 100 μl/well TMB was added and the plates incubated until sufficient color change has been reached (usually around 5 minutes). 100 μl/well 2M sulfuric acid was then added to stop the reaction and the plate read at OD450 on a Spectramax. In some cases, Human IgG Fc (Jackson ImmunoResearch #009-000-008) was added at 100 μg/ml to both the blocking agent and the primary antibody.

In a representative S. aureus Cell ELISA (FIG. 27), a number of antibodies were tested for binding to S. aureus (Newman stain) and a SpA deficient S. aureus strain (ΔSpA) in the presence and absence of human IgG1-Fc used to block non-specific binding and IgBP medicated Fc binding. Test Antibodies include anti-SpA MAB1 and anti-SpA variant MAB2, anti-ClfA Parental MAB, anti-RSV variant MAB5 and a non-specific anti-KLH antibody.

Discussion of ELISA Results:

The ELISA results are shown in FIG. 27. These results indicate that the control (anti-KLH) and parental antibodies (non-variant antibodies) have high non-specific binding to S. aureus Newman stain (lower panels). This non-immune binding is reduced by include human IgG1-Fc as a blocker (FIG. 27, right panels) (for example see anti-KLH and anti-ClfA antibodies). This is presumably due to blockage of IgBP Fc binding sites on the S. aureus Newman stain (FIG. 27 right panels). This is supported by the finding that the anti-RSV variant antibody (MAB5) does not bind to S. aureus Newman stain in the absence or presence of blocking human IgG1-Fc FIG. 27; lower panels). Thus, mutations introduced into the heavy chain constant region of variant MAB2 and MAB5 eliminate Fc binding of the variant antibodies to S. aureus cell surface IgBPs. In contrast, both the anti-SpA parental and anti-SpA variant antibodies bind strongly to S. aureus Newman stain in the absence or presence of blocking human IgG1-Fc (FIG. 27, lower panels), demonstrating variable domain binding by the anti-SpA antibodies. The variant anti-RSV antibody had minimal background binding whereas the variant anti-SpA antibody had significant binding.

The variant anti-SpA and anti-RSV antibodies (MAB2 and MAB5) have no binding to SpA deficient Staph (FIG. 27, upper panels). However, Fc mediated binding of the parental anti-SpA, anti-ClfA and anti-KLH antibodies are seen that can be blocked by human IgG1-Fc (FIG. 27, Upper left panel). This may be due to binding by alternative IgBPs expressed by the ΔSpA strain, such as S. aureus Sbi,

The results shown in FIG. 27 are tabulated in FIG. 28. These results indicate that the heavy chain constant region mutations in MAB2 and MAB5 eliminated non-specific binding and SpA Fc medicated binding. The specific binding of the anti-SpA heavy chain constant region variant demonstrated variable domain binding of this antibody to SpA. Additionally, IgG1Fc did not compete with anti-SpA antibody binding to SpA, demonstrating that the region of SpA recognized by the variable domain of anti-SpA antibodies MAB1 and MAB2 do not overlap with the SpA-Fc binding sites.

Example 12: FACS Analysis of Antibody Binding to S. aureus

Binding of the parental anti-SpA antibody (MAB1), an example anti-SpA variant antibody (MAB2) and a heavy chain constant region matched anti-RSV variant control antibody (MAB6) were investigated by FACS, using Staphylococcus aureus Newman stain (FIG. 29; upper panels) or a ΔSpA strain (FIG. 29, Lower panels)) grown in log phase (FIG. 29, left panels), or from stationary phase cultures (FIG. 29; right panels). Standard FACS methods known in the art were used for the analysis. The second antibody used in the study was Alexa Fluor 488 conjugated Fab goat anti-human IgG. As can be see in FIG. 29, the control anti-RSV variant antibody did not bind to S. aureus under all conditions tested, confirming that the heavy chain constant region variant chain does not bind to S. aureus FcBPs via its Fc domain. This confirms the data seen in cellular ELISA assays. In contrast, the parental and variant anti-SpA antibodies (MAB1 and MAB2) bound strongly to S. aureus from stationary or log phase cultures, but not to the ΔSpA strain of S. aureus. This result confirms that antibody binding by the variant anti-SpA antibody (MAB2) is mediated by the variable domain of the antibody.

Effector Function Testing of Variant Antibodies

In a variety of in vivo and in vitro settings, antibody coating of targets has been shown to mediate potent killing mechanisms such as complement-dependent cytotoxicity (CDC), antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP) and opsonophagocytosis. These effector functions are mediated by the antibody heavy chain constant region. To verify that variant antibodies described herein do not have attenuated effector function, due to the introduction of mutations that attenuate bacterial IgBP binding, antibodies can be tested in a number of binding assays (FcγRs and C1q binding) and effector function assays (Complement deposition opsonophagocytosis, CDC, ADCC, ADCP, anti-microbial activity),

Construction, Expression, and Purification of FcγRs: FcγR binding of Fc variant antibodies: FcγRs can be constructed as C-terminal-6×His-GST fusions, expressed in 293T (human FcγRs) cells, and purified by using nickel affinity chromatography. Detailed methods are provided in Lazar et al., 2006.

FcγR binding of parental and Fc variant antibodies: Variants are constructed, expressed and purified, and can be screened for FcγR affinity by using an AlphaScreen assay. AlphaScreen assays can use untagged variant IgG1 to compete the interaction between biotinylated IgG bound to streptavidin donor beads and FcγR-His-GST bound to anti-GST acceptor beads.

True binding constants can be obtained by a competition surface plasmon resonance (SPR) experiment. Competition SPR experiments measured capture of free Ab from a preequilibrated Ab/receptor analyte mixture to V158 FcγRIIIa-His-GST bound to an immobilized anti-GST surface. Equilibrium dissociation constants (K_(D) values) are calculated by using the proportionality of initial binding rate on free Ab concentration in the Ab/receptor equilibrium. Detailed description of AlphaScreen and SPR assays is provided in Lazar et al., 2006 and references therein. SPR measurements were performed using a BIACore 3000 instrument (GE Healthcare). Fcγ R affinity can be determined as described in Nieba et al., 1996.

C1q binding of parent and variant antibodies: Surface plasmon resonance determination of binding affinities. SPR measurements can be performed in HBS-EP running buffer (10 mM HEPES pH 7.4, 0.15 M NaCl, 3 mM EDTA, 0.005% v/v surfactant P20, GE Healthcare) using a BIACore 3000 instrument (GE Healthcare).

For determining C1q affinity of IgG1K antibodies and their variants, a Protein L CM5 biosensor chip (GE Healthcare) can be generated using a standard primary amine coupling protocol. The chip's reference channel can be coupled to bovine serum albumin (BSA) to minimize nonspecific binding of C1q. Antibodies at 50 nM can be immobilized on the protein L surface for 0.5 or 1 min at 10 μL/min. C1q in 2-fold serial dilutions (starting at 100 or 25 nM, 5 concentrations total) is injected over antibody-bound surface for 3 min at 30 μL/min followed by a 4.5 min dissociation phase. C1q molarity can be calculated using the molecular weight of the C1q hexameric bundle, 410 kDa. After each cycle, the surface can be regenerated by injecting glycine buffer (10 mM, pH 1.5). In order to subtract nonspecific C1q binding to antibody-coated protein L surface, an Fc variant with greatly ablated CDC activity can be included. Sensorgrams can be processed by zeroing time and response before the injection of C1q and by subtracting appropriate nonspecific signals (response of BSA-blocked reference channel, response of an Fc variant with ablated CDC, and response of running buffer). Kinetic parameters can be determined by global fitting of association and dissociation phase data with a two-state binding model (A+B AB AB*). K_(d) was calculated as K_(d1)/(1+1/K<_(d2)).

ADCC of Parent and Fc Variant Antibodies.

ADCC can be measured by using either the DELFIA EuTDA-based cytotoxicity assay (PerkinElmer) or the LDH Cytotoxicity Detection Kit (Roche Diagnostics). Human PBMCs can be purified from leukopacks by using a Ficoll gradient and allotyped for V/F158 FcγRIIIa by using PCR. NK cells can be isolated from human PBMCs by using negative selection and magnetic beads (Miltenyi Biotec, Auburn, Calif.). Target cell lines can be obtained from American Type Culture Collection. For Eu-based detection, target cells are first loaded with BATDA [Bis(acetoxymethyl)-2,2′:6′,2″-terpyridine-6,6″-dicarboxylate] at 1×10⁶ cells per ml and washed 4×. For both Eu- and LDH-based detection, target cells can be seeded into 96-well plates at 10,000 cells per well and opsonized by using Fc variant or WT Abs at the indicated final concentration. Triton X-100 and PBMCs alone can be run as controls. Effector cells can be added at 25:1 PBMCs:target cells or 4:1 NK cells:target cells, and the plate are incubated at 37° C. for 4 h. Cells are incubated with either Eu³⁺ solution or LDH reaction mixture, and fluorescence can be measured by using a Fusion Alpha-FP (PerkinElmer). Data can be normalized to maximal (Triton) and minimal (PBMCs alone) lysis and fit to a sigmoidal dose-response model.

ADCP of Parent and Fc Variant Antibodies.

For phagocytosis experiments, monocytes can be isolated from human V/F158 FcγRIIIa PBMCs by using a Percoll gradient and differentiated into macrophages by culture with 0.1 ng/ml granulocyte/macrophage colony-stimulating factor for 1 week. For quantitative ADCP, target cells (e.g. WIL2-S for anti CD20 antibody Fc variants) can be labeled with PKH67, seeded in a 96-well plate at 20,000 cells per well, and treated with WT or variant Ab at the designated final concentrations. Macrophages are labeled with PKH26 (Sigma) and added to the opsonized labeled target cells at 20,000 cells per well, and the cells are co-cultured for 18 hours. Fluorescence is measured by using dual-label flow cytometry.

CDC of parental and Fc variant antibodies can be tested initially in the context of an anti CD20 antibody as described in Moore et al., 2010. For CDC assays, target Ramos or Raji cells can be washed 2× in RHB Buffer (RPMI Medium 1640 containing 20 mM HEPES, 2 mM glutamine, 0.1% BSA, pH 7.2) by centrifugation and resuspension and seeded at 40,000 cells per well. Native IgG1 or variant antibody is added at the indicated final concentrations. Human serum complement (Quidel, San Diego, Calif.) are diluted with RHB buffer and added to opsonized target cells. Plates can be incubated for 2 hr at 37° C., Alamar Blue is added, cells are cultured overnight, and fluorescence is measured in relative fluorescence units. Data is normalized to maximal (Triton X-100) and minimal (complement alone) lysis and fitted to a sigmoidal dose-response curve.

FcRn binding of variant anti-SpA antibodies: FcRn binding can be measured as described previously (Dall'Acqua et al., 2006; Datta-Mannan et al., 2006).

Anti-S. aureus effector function can be tested in a number of in vitro assays. These assays may include a C1q deposition, C3 deposition, bacterial opsonophagocytic assays and bactericidal assay, which are described below.

Example 13: Anti-S. aureus C1q Deposition Assays of Selected Antibodies and their Fc Variants

C1q Deposition Assay:

This assays tests for the ability of antibodies to deposit complement on bacteria. Add 100 μl of bacteria (@ OD600 1.0) to microtubes washing 1× with 1 ml HBSS+, Centrifuge at ˜7000×g (9000 rpm), for 5 minutes at 4° C. Next, add 50 μl I of a 2× concentration of test antibody or isotype control diluted in GV buffer. Add 50 μl of human complement @ 20% diluted in GV buffer for a 10% final concentration. Incubate samples at 37° C. in shaking water bath for 60 minutes, then wash 2× with 1 ml HBSS+, ˜7000×g (9000 rpm), for 5 minutes at 4° C. Add 100 μl of a mouse anti-human C1q mAb, or C1q isotype control for a final concentration of 3 μg/ml in GV buffer, incubate for 30 minutes @ 4° C. Next, wash 2× with 1 ml of HBSS+].

FACS detection of complement on bacteria: Add 100 μl of anti-mouse IgG-PE at a 1:50 dilution in HBSS+ at 4° C. Incubate for 30 minutes, in the dark, on ice with shaking. Wash 2× with 1 ml HBSS, ˜7000×g (9000 rpms), for 5 minutes at 4° C. Resuspend in 0.5 ml of HBSS+, at 4° C. Transfer samples to FACS tubes. Analyze samples by Accuri gating on bacteria, 10,000 events, FL2.

Reagents: HBSS+: w/Mg Ca. #14025-092, Gibco; Gelatin veronal buffer (GV), # G6514, Sigma; Human Serum Complement # A113, Quidel—(thaw rapidly in 37° C. water bath to ˜90% leaving small pellet, mix and put on ice, aliquot and store at −80° C.); Mouse-IgG1 anti-human C1q antibody (1.1 mg/ml), # A201, Quidel; Negative control for anti-human C1q Mab: Anti-TNP mouse IgG1 (isotype control for C1q mAb), NA/LE, clone 107.3, stock=1.0 mg/ml, #554721, BD Pharmingen; PE-conjugated F(ab′)2 fragment donkey anti-mouse IgG (H+L) antibody, #715-116-150, Jackson Immuno Research—(rehydrate with 1.0 ml distilled water and add 20 μl of stock per 980 μl of HBSS+=1:50 dilution); Distilled water, #15230, Gibco.

Results: C1q deposition assays were performed to test whether the parental anti-SpA (MAB1), its variant anti-SpA (MAB2), and the control anti-RSV variant (MAB5) antibodies are able to can deposit C1q on wild type S. aureus Newman and a S. aureus ΔSpA strain (FIG. 30). A dose titration of the test antibodies was performed using S. aureus WT and ΔSpA Newman strain in the presence of pooled human serum as a source of complement. As shown in FIG. 30a , the variant anti-SpA antibody (MAB2), deposits C1q on the surface of the wild type S. aureus Newman strain in a dose dependent manner, while the parental anti-SpA antibody (MAB1) and negative control anti-RSV variant antibodies (MAB5) lack this function (FIG. 30a , upper panel). The ability of the anti-SpA variant antibody (MAB2) to deposit C1q on S. aureus is lost in assays using the ΔSpA S. aureus stain, which has no SpA expression (FIG. 30b ). This result demonstrates that the anti-SpA variant antibody shows antigen dependent deposition of complement on the S. aureus Newman strain. This demonstrates that FcBPs expressed by S. aureus are able to neutralize the C1q effector function of the parental IgG1 antibodies, but not that of its variants such as MAB2. The FACS data from FIG. 30 is tabulated in FIG. 31.

Example 14: C3 Complement Deposition Assay

C3 deposition was determined using S. aureus stain JE2 and measured by FACS. The following methods were used. Staph JE2 was grown overnight in THB at 37° C. with shaking. Next day, stationary phase culture were washed and resuspended in PBS to OD_(600 nm)=0.4. Aliquot 1 ml of bacterial culture into eppendorf tubes and spin at max speed for 2 min, then resuspend the pellet in 50 μl of HEPES buffer (120 mM HEPES, 140 mM NaCl, 5 mM CaCl₂ and 25 mM MgCl₂). Dilute pooled human serum to 10% in HEPES buffer. Add 50 μl of 10% serum to the bacteria.

Add anti-SpA parental (MAB1) or variant antibodies (MAB2) at a final concentration of 2 μg/ml. Incubate for 30 min at 37° C. Spin max/2 min, Wash 1× with 1 ml of 0.1% BSA+PBS, then resuspend in 100 ul of αC3b (diluted 1:200 in 0.1% BSA+PBS (Protos Immuno Research)). Incubate for 20 min at 4° C. and then wash as described above. Resuspend in 500 μl of PBS and analyse using FACS (FIG. 32).

Results: As can be seen in FIG. 32, the anti-SpA parental antibody was unable to deposited C3 on the surface of S. aureus JE2 (Control-black vs MAB1—Red). In contract, the anti-SpA variant antibody resulted in strong C3 deposition of the surface of S. aureus JE2 (MAB2-green). This result reinforces that data seen for C1q deposition, and demonstrates that S. aureus interacts with the heavy chain constant region of parental antibodies, blocking their effector function. This interaction is presumably mediated by S. aureus IgBPs including SpA. In contract, variant antibody MAB2 maintains its effector function as demonstrated by robust C1 q and C3 deposition on the surface of S. aureus SpA expressing stains.

Example 15: Neutrophil-Mediated Opsonophagocytic Assay

An opsonization assay may be a colorimetric assay, a chemiluminescent assay, a fluorescent or radiolabel uptake assay, a cell-mediated bactericidal assay, or any other appropriate assay known in the art which measures the opsonic potential of a substance and thereby identifies reactive immunoglobulin. In an opsonization assay, an infectious agent, a cell, and the opsonizing substance to be tested are incubated together.

In certain embodiments, the opsonization assay is a cell-mediated bactericidal assay. In this in vitro assay, an infectious agent such as a bacterium, a phagocytic cell, and an opsonizing substance such as immunoglobulin, may be incubated together. Any eukaryotic cell with phagocytic or binding ability may be used in a cell-mediated bactericidal assay. In certain embodiments, phagocytic cells are macrophages, monocytes, neutrophils, or any combination of these cells. Complement proteins may be included to promote opsonization by both the classical and alternate pathways.

In one method, the ability of parental and variant anti-SpA antibodies and control antibodies were evaluated for the ability of example test antibodies to mediate the phagocytosis of opsonized bacteria labeled with FITC.

The following method was performed: Resuspend FITC labeled bacteria in 1 ml cold OPA buffer (HBSS Ca++& Mg+++0.2% BSA) at ˜4.0E+08 CFU/ml. Opsonize with specific antibodies or control. Add 100 μl of Mab in OPA buffer to bacteria-FITC pellet (see above) for 30 minutes, 37 C shaking water bath. Aspirate dry, keep on ice in dark until phagocytosis assay set up. Add 100 μl of washed PMNs at 10E+06/ml (1.0E+06/tube) to opsonized bacterial cell pellet in mirotube, transfer to 12×75 mm polypropylene FACS tube. Incubate in 37° C. shaking H₂O bath for 30 minutes. Next, add 100 μl of cold quench/tube (to quench the staining of any externally bound bacteria) vortex, add 2 ml of cold AB. Spin for 5 minutes at 1,200 rpm, 4° C. Decant supernatant and wash again with 2 ml of AB, 4° C. Add 0.5 ml of AB/tube (4° C.) read on Accuri, collect 5000 events, FL1. Reagents: OPA buffer: HBSS Ca++& Mg+++0.2% BSA; AB: Dulbecco's DPBS-+2% FBS: Quench: Trypan blue (Gibco #15250-061) diluted 1:3 in DPBS—(1 ml trypan blue and 2 ml PBS): HBSS: Mg++Ca++, Gibco, #14025-092; DPBS: no Mg++Ca++, Sigma # D8537 or Lonza/BioWhittaker #17-512Q

Phagocytosis Results: The anti-SpA parental antibody (MAB1) and an example variant anti-SpA antibody (MAB2) were tested in two phagocytosis assay (FIG. 33 and FIG. 34). In the first assay (FIG. 33), two control antibodies were used (an anti-RSV variant (MAB5) and a non-specific parental anti-KLH antibody). S. aureus Newman stain and a ΔSpA strain lacking SpA expression were used at the target bacteria. As shown in FIG. 33, the anti-SpA variant antibody was able to enhance the phagocytosis of the S. aureus wild type Newman strain as compared to control antibodies. The control antibodies were able to induce some non-specific uptake. The parental anti-SpA antibody gave a similar results as the control antibodies, demonstrating that S. aureus is able to suppress the effector function of the parental ant-SpA antibody (MAB1), but not that of its variant (MAB2). No enhancement of phagocytosis was seen using the ΔSpA S. aureus strain, demonstrating variable domain specificity of the enhanced effector function of the anti-SpA variant antibody MAB2.

In a second opsono-phagocytosis assay format, anti-SpA MAB 1 and 2 (variant) were tested (FIG. 34). The opsonic ability of an antibody is determined by the amount or number of infectious agents remaining after incubation. The fewer the number of infectious agents that remain after incubation, the greater the opsonic activity of the antibody tested. In a cell-mediated bactericidal assay, opsonic activity is measured by comparing the number of surviving bacteria between two similar assays, only one of which contains the antibody being tested. Alternatively, opsonic activity is determined by measuring the number of viable organisms before and after incubation with a sample antibody. A reduced number of bacteria after incubation in the presence of antibody indicates a positive opsonizing activity. In the cell-mediated bactericidal assay, positive opsonization is determined by culturing the incubation mixture under appropriate bacterial growth conditions. Any reduction in the number of viable bacteria comparing pre-incubation and post-incubation samples, or between samples, which contain immunoglobulin, and those that do not, is a positive reaction. As can be seen (FIG. 34) the variant anti-SpA antibody (MAB2) resulted in significant enhanced opssonphagocytic activity as measured by bacterial survival when compared to the Parental MAB1. The control represents bacterial survival in the absence of added antibody.

Example 16: Neutrophil-Mediated Opsonophagocytic Bactericidal Assay

Opsono-phagocytic killing of S. aureus JE2 using pooled human serum. The following assay was used to test parental and variant anti-SpA antibodies for their effect on the opsonophagocytic killing of S. aureus JE2

Bacteria were grown overnight in THB. In the morning dilute cultures 1:40 in fresh THB and grow to OD_(600 nm)=0.4. Pellet S. aureus at @ 4000 rpm for 10 min then wash in 10 ml of PBS. Centrifuge as above and resuspend in 300 ul of PBS. Adjust to the OD_(600 nm)=0.4 in 3 ml of PBS. Dilute bacteria1:5 in pooled human serum using siliconized tube. Test antibodies (MAB1 and MAB2) were added to tubes at a final concentration of 5 μg/ml and 25 μg/ml. Tubes were incubated at 37° C. for 30 min, then diluted 1:40 in RPMI. 100 μl of bacteria were added to 100 ul of neutrophils (MOI=0.5) in 96 well tissue culture plates, spun at 1600 rpm for 5 min and incubate at 37° C.+CO₂ for 30 min. After 30 min, serial dilutions were made in molecular grade water and then plated on THA plates.

Results: It can be seen from FIG. 35 that there was a significant increase in opsonophagocytic killing of S. aureus JE2 by the variant anti-SpA antibody as compared to the parental anti-Spa antibody.

REFERENCES

The references, patents and published patent applications listed below, and all references cited in the specification above are hereby incorporated by reference in their entirety, as if fully set forth herein.

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What is claimed is:
 1. An anti-Clumping Factor A (Clfa) variant IgG antibody comprising: a light chain variable domain and a heavy chain variable domain comprising an antigen recognition region having antigen-specific immune binding to S. aureus protein A (Clfa), wherein the light chain variable domain comprises SEQ ID NO:29 and the heavy chain variable domain comprises SEQ ID NO:28; and a variant immunoglobulin heavy chain constant region that differs from that of a parent heavy chain constant region by one or more amino acid substitutions, wherein the parent heavy chain constant region includes a CH1 sequence comprising SEQ ID NO:68, a CH2 sequence comprising SEQ ID NO:76, and a CH3 sequence comprising SEQ ID NO:80; wherein the one or more amino acid substitutions comprise: (i) a substitution of H at EU position of 435 with an R (H435R) and a substitution of Y at EU position of 436 with an F (Y436F); and (ii) an amino acid substitution that attenuates non-immune binding of S. aureus Fc binding protein, SSL10.
 2. The anti-Clfa variant IgG antibody of claim 1, wherein the anti-Clfa variant IgG antibody is a monoclonal antibody of any isotype.
 3. The anti-Clfa variant antibody of claim 1, wherein the anti-Clfa variant IgG antibody is a chimeric, humanized, or human anti-Clfa Fc variant IgG1 antibody of any allotype or isoallotype.
 4. The anti-Clfa variant antibody of claim 3, wherein the one or more amino acid substitutions results in alteration of the human IgG1 allotype.
 5. The anti-Clfa variant antibody of claim 3 wherein the CH3 domain, or a portion of the CH3 domain of the parent heavy chain constant region, is replaced with a homologous sequence from an IgG3 of any allotype or isoallotype, resulting in an anti-Clfa variant antibody of mixed isotype.
 6. The anti-Clfa antibody of claim 3, wherein the variable light chain sequence, the variable heavy chain sequence, or both, further comprise one or more maturation mutations resulting in one or more amino acid substitutions, deletions, or insertions that improve one or more properties of the humanized anti-Clfa antibody selected from affinity, avidity, stability, solubility, expression level, and/or biological activity.
 7. The anti-Clfa variant IgG antibody of claim 1, wherein the amino acid substitution that attenuates non-immune binding of SSL10 is: a substitution of K at EU position 274 with a Q (K274Q); a substitution of N at EU position 276 with a K (N276K); or a substitution of K274Q and N276K.
 8. The anti-Clfa variant IgG antibody of claim 1, wherein the anti-Clfa variant IgG antibody binds via constant region non-immune binding to Protein G, Protein L, or both, but does not bind to SpA or Sbi by interaction with the heavy chain constant region of the variant antibody.
 9. The anti-Clfa variant IgG antibody of claim 8, wherein the constant region non-immune binding to Protein G, Protein L, or both, is used to affinity purify the anti-Clfa variant antibody. 